The advice about going into a vape shop and chatting with the staff is spot on IMO if your'e not sure about what you want, along with watching some YT reviews to help get a better idea. While your'e doing that you might be able to whittle it down to a short list and take that further in the shop. I'd definitely suggest sticking to a single coil RDA to start off, unless your'e set on a dual coil. That way you're only worrying about one coil, not balancing two. Also look for something that's easy to build on. The YT video will give some idea, but bear in mind quite a few reviews are little more than infomercials where everything is "dead easy" and "tastes great". Some of the reviewers also perhaps forget what it's like to start off and of course, with years under their belt, almost anything is a dead simple build deck. Case in point is the Peerless RDA which is quite often rated as an easy enough deck by some reviewers, bit of a pig in real life though, too much of a juggling act.
Another thing to consider is how often you want to be dripping, if you'd rather it be less than more, you might want to look at RDAs with slightly deeper juice wells. There's several current and really good single coil drippers that are dead easy to build on and produce great flavour such as the Recurve and Nudge 22. The recently released Drop Solo also looks appealing (and has the deep juice well - the Nudge and Recurve can be used as drippers but IMO are more suited to squonking as their juice capacity isn't that great, certainly usable though). The Pulse 22 is another very good single coiler, deep well again. Coil placement can be a bit fickle but it doesn't take too long to work out. All of these RDAs are highly rated for a reason and it's not just hype. No need to complicate things too much by pondering loads and loads of 'also-rans' IMO.
Personally I find drippers work better with fancier coils but certainly do-able with single wire coils. Decent frame stapled aliens or fused claptons can be had for not too much money. Just try to make sure that any fancy coils you buy are around the 0.25 ohm or above (they will be in the lower resistance range due to the numbers of wires involved in their make up). For building I'd just start with something like 26 gauge wire. You can also decide between Kanthal, stainless steel and NiCr 80 wire. I prefer NiCr 80. It has a quicker ramp up time (sitting between Kanthal and stainless) and has a cleaner taste IMO. Wires beyond (e.g. smaller than) 28 can get a bit fiddly if you're not used to it, and esp those in the 30-34 range! Below 26 / 24 and you can start to hit some problems with resistance being too low if your'e not careful and not sure what you're doing. Just keep it simple. 26 gauge 6-8 wrap 3mm diameter coils coming somewhere within the 0.5 - 1.2 ohm range depending on the wire and number of wraps.
You don't need a tool kit but it can work out cheaper in the long run, plus you get the case to keep the stuff in. Coilmaster also do a very good DIY Mini kit that has the lot. A coil jig at least does make life much easier, as do angled tweezers, wire cutters and small precision screwdrivers. An ohm meter is a very good idea too. Good idea to keep a pair of small scissors exclusively for cotton too.
Good luck
+1 on all of that - for reference when I suggested the coilmaster set it's going to be useful from start to finish. From a personal standpoint I don't see the benefit in getting one or two tools and then having to get the rest further on down the track. That is definitely one of the things that taking the plunge has more benefit.
