turbo e21 possible

I was going to get an e30 but It all didn't pan out so im looking at a e21 right now. My question is, I want more power, what would be the best ,engine swap or turbo it? I have about a 5000 grand budget. Ive searched but couldn't find anything

I'm assuming you have the 320i (4 cylander) motor, you might want to look at the m44 motor, it was used in the e36 318i. They produced 142hp and you don't have to do any major modifications (I haven't done this so I'm speaking theoretically) to put that motor in, the other option would be the s13 motor out of an e30 m3, 192hp but much harder to put your hands on, and may blow your budget just for a good motor. You can also look up performance upgrades for the m44 motor, being newer and far more common, there are undoubtedly upgrades available.

Upon looking at the m44 engine (in my 318ti) and looking at the old 245 getrag transmission I still have, you would have to use an e36 transmission as well. This causes problems for your speedometer, because there is no cable drive from the e36 transmission. You could modify the rear subframe and put in an e30 rear end and change out your instrument cluster but now we are talking a lot of custom fabrication and work.
The m3 motor is based on the m10 block so it should bolt right up. Electronics is another matter, but any engine update will require that.