What scale are you interested in... 1/10 or 1/8?
"Bang for the buck" is a relative term... while you can get into the hobby a lot cheaper with a RTR, there are tons of hidden expenses where you will end up buying twice if you get an RTR and may end up spending more money than if you would've bought a race grade kit in the first place. More info here:
Which 1/10 4WD SCT is best?
I realize your'e probably not interested in the SCT class, but many of the brands discussed on that thread will be universally compared across other classes they support.
If you're looking for a 1/10 buggy, then I would highly recommend PR Racing kits, in fact you can get a really good deal on the older 401LW which is forward compatible with all the Type R parts if you wanted to upgrade it:
If you're looking for a 1/8 buggy, then I would consider ARRMA for decent entry level which can keeps initial costs down and will need minimal upgrades, a higher quality RTR would be Serpent, but if I were to build a 1/8 kit for myself today, I would build a TEKNO.