Well, trading is banned. So you can't get Alakazam or Golem or Machamp or Gengar, all of which would be pretty good solos. But alas, you are unable to get said Pokemon. This also disallows trading over already leveled Pokemon/Pokemon that have good moves already.
You also can't use in game glitches, so no Mew or missingno. I think you can still use the Pokedoll glitch though for some reason. If you can't, then Haunter very well might be on the list of Pokemon usable.
Um, I think there's something like EVs in R/B, but they're called something like DVs for Deter Values or something weird. Vitamins can raise a stat up to 1/3 of its max if that makes sense. We will probably want to buy some of the +Spd ones so we can hopefully outspeed the Alakazams and Gengars. Maybe get some +Spe too. I don't know though, that's far into the future.