If you're looking to get a good DS with the clamshell design but don't want to empty your wallet, turn your attention to the 2DS XL which was recently announced (Not sure if it came out yet). Great budget console and is capable of playing all of the gen 4 Pokemon games and beyond (Up to the current gen 7).

Also, fair warning: Pokemon has a LOT of depth to it beyond the move choosing and such. Prepare for a wall of text.

There is an enormous competitive community in which players experiment with certain Pokemon with moves and stats, then form a meta to go with it. Certain Pokemon are naturally better than others (OU, or overused, is the most commonly used format), while some are too good for regular play (Ubers is a rarely-used format saved for most legendaries due to their unfair stats, while the M-Rayquaza tier is a tier above ubers saved exclusively for the ridiculously overpowered Mega Rayquaza), and some are so bad that no one ever uses them (The PU tier, which doesn't stand for anything but is just an expression that you may be familiar with).

In addition, Pokemon have sorts of "Genetics" that make them different than others of their species. Some Pokemon are better straight out of the egg. These are called IVs and are one of the many values that can be controlled by breeding. The values range from 0 to 31, and the higher the value, the more stats the Pokemon will gain from leveling up. This means a Pokemon's base stats may be different from their actual stats.

Another value can be used for making a Pokemon have better stats than normal, and unlike IVs are not controlled by breeding. They're called Effort Values, or EVs (Not to be confused with the Pokemon Eevee), and you get them by defeating certain Pokemon. Every 4 EVs will grant another stat point (Usually; this is just a rule of thumb.), so if you plan on training a Pokemon's EVs, stick to multiples of 4. For every pokemon, the maximum effort value total is 510, and for each stat the maximum is 252. This means you'll have to plan your training regimens very carefully for your perfect critter. If you screw up your math, though, you're able to feed your Pokemon certain berries that increase their friendship while lowering their effort value of a certain stat depending on the berry.

This is all I can tell you for now. Feel free to ask me for more info, since I'm happy to help.