On a ‘standard’ acoustic kit, snares tend to be 14” diameter, and toms are 10”, 12” and 14” for a ‘fusion’ kit, or 12”, 13” and 16” for a ‘rock’ kit. Electric kits invariably have much smaller drum sizes all round (since the sizes have nothing to do with the sounds produced like they do on acoustic kits) - just be careful to not to go too small as it can become hard to hit the drums accurately (eg with a 6” tom pad)! As a drum teacher I'd say buyer 1. should look for a minimum 10” snare with 8” toms, but a 12” snare and 10” toms may be preferable for buyer 2. The kick pad’s size is less important, since it is struck with a pedal-operated beater (which is fixed in place, so striking accuracy is not an issue) - just consider if it is big enough to accommodate a double kick drum pedal (with two side-by-side beaters), should you perhaps want to learn to play fast metal ‘blast beats’ and the like during my drum lessons - now or at some point in the future!  

Sadly, these are an inevitability, since manufacturers are yet to come up with a viable alternative at anywhere near approaching a reasonable cost. The softer the rubber the better for playing comfort/lack of noise, but unfortunately only the more expensive kits from Roland or Yamaha seem to have softer cymbals. Without testing them first, you need to rely solely on reviews to asses this. Be prepared for cymbals on electric kits to be the biggest compromise on feel/noise, if you don’t want to spend a fortune! They bear little resemblance to playing the actual acoustic cymbals you'll play in my drum lessons (which of course are made out of metal), and as they’re much thicker, are generally much heavier in weight, so ‘swing’ a lot slower when struck. 

Real acoustic hi-hats are comprised of two cymbals, one upside-down to the other, which open and close by operating a foot pedal. As well as feeling nothing like them to strike (being rubber), at the lower end of the budget spectrum electric hats are simply one rubber pad fixed in place, that does not move up and down (instead the foot pedal simply triggers a ‘closed’ or ‘open’ sound depending on if it’s pressed down or not). Of course, this makes it feel even less realistic to play, but as a drum teacher I can advise that in practice it's a compromise that can be lived with quite happily. At the upper end of the budget range, more advanced electric hats have one pad that moves up and down (which feels closer to a real hi hat), or even two pads that move apart just like an acoustic set of hi hats (though since you don’t strike the lower cymbal, this is largely overkill), and you could potentially upgrade your hi hat to this type, but from the leading manufacturers these are VERY expensive - a Roland VH-10 or VH-11 for example, will set you back around £250-300, and you also need to buy a standard acoustic kit type hi-hat stand (£50-100 depending on quality), so this sort of feature is probably best left to buyer type 3. Thomann do also now supply their own brand Millenium MPS-750X single hi-hat pad, that moves up and down and even comes with a stand, at a super low price of £66 delivered, but again compatibility with your particular kit may be an issue, so try to ask first. 

When struck, pads send information to the sound module, which then triggers a sound assigned to that pad. Single or ‘mono’ zone drum pads are only capable of triggering one sound – that might be fine for a tom, but not so for a snare (for buyers 1. and 2.). 

In order to be practically useful, you need to be able to play 2 (or ideally 3) different types of stroke on the snare: ‘standard’ using the tip of the stick on the centre, and ‘cross stick’ - lying the stick on its side and using the shaft to play ‘clink’ type sounds on the rim. More advanced players may also want to play ‘rim shots’, where you simultaneously strike the centre with the tip of the stick and the rim with the shaft of the stick, which on an acoustic kit creates a loud ‘crack’ accented snare sound. Dual zone pads have a second sensor in the rim, capable of triggering another sound – essential for playing ‘cross stick’ strokes on snare. They may also allow for ‘rim shots’ - check to see if the sound module supports this. 

As a drum teacher, I advise that a ride cymbal pad really needs to be a minimum of dual zone, but preferably tri zone. This is because you need to be able to reproduce the ‘ping’ sound heard when playing the ‘bell’ (raised dome in the centre), of an acoustic ride cymbal, as well as ‘tah tah tah’ sounds when using repeated strokes on the ‘bow’ (between the bell and the edge). Dual zone ride cymbals tend to have a ‘bell’ for show only (no sensor), with one sensor in between the bell and the edge (which can be played instead of the bell, with a ‘ping’ sound assigned to it) and a second sensor on the edge (which can be played instead of the bow, with a ‘tah’ sound assigned to it!). In order to work on the material I teach in my face-to-face drum lessons, as well as my 1-to-1 online drum lessons, this is necessary for buyer 1. wanting to learn proper technique, and acceptable for buyer 2., but does mean you will use the ‘shoulder’ of the stick for ‘tah’ sounds, whereas on an acoustic ride you would use the tip!  

There is potentially a ‘sneaky’ way to upgrade a cheap kit, supplied with single zone cymbals, to have a dual zone ride & achieving the desired separate ‘bell’ sound. If the sound module has one or more extra trigger inputs (unused by the supplied drums & cymbal pads, designed to enable you to expand the kit adding extra pads), you could use a ‘Y’ splitter cable to take the stereo jack output from your new dual zone ride, to two separate mono jacks, connecting one to the existing ride input for ‘tah tah’ bow sounds, and the other to one of the spare inputs, assigning a bell sound to that (provided there are bell sounds onboard!).   

A decent kick pedal will become more and more important as you improve your playing proficiency and attempt to apply the skills you'll learn in my drum lessons, playing kick drum strokes at increasingly smaller intervals! There are broadly 2 types: single chain and double chain mechanisms (ignoring more ‘specialist’ belt/direct drive or magnetic models). This refers to a short length of ‘single’ or double’ bicycle type chain that attaches the foot pedal to the beater. As the ‘toe’ part of the foot pedal mostly wobbles side-to-side (making it difficult to play two kick drum strokes in quick succession), cheap single chain kick drum pedals are tolerable for buyer 1. but will likely need upgrading in a year or two. For playing accuracy and stability, and to avoid the need for future upgrades, any drum teacher would say buyer 2. should aim for a double chain kick drum pedal. Be sure not to confuse this with a ‘single pedal’ or ‘double pedal’, which instead refers to whether you have one kick drum pedal and beater (for one foot, as standard), or two pedals and beaters (to play the kick drum with both feet)!   

The other thing can really affect the stability of the ‘heel’ part of the pedal, is the design of the underside – those with a solid metal floor or ‘base’ plate (front to back), are far superior to those with a ‘bent rod’ or ‘thick wire’ type frame, and are worth the extra few £’s.  

These may be suitable for buyer 1. or just to get going cheaply, though it’s rare that all items will be of high quality - note here neither the pictured headphones nor pedal feature the desirable designs outlined above, and I doubt the foam on the stool is thick! 

As a drum teacher, I'm always saying in my drum lessons that a great advantage to buying a second-hand kit, is that sellers often throw in a kick pedal, stool etc, which can offer a significant saving, since in many cases they may have quit drumming altogether and have no use for these. If not mentioned, ask if they’re included - if they are, ask for the make and model of the kick pedal before agreeing to buy. Look it up online - is it any good? If so great, if not - there’s little point paying for that too (it would just need instantly replacing/upgrading), when you could ask for a discount to not include it, and instead put that money towards a decent one! 

When buying new, always look for ‘bundle deals’ where kick pedal, stool, headphones etc are included in the price of the kit (if they look decent) - this can offer a significant saving compared to buying them individually.