Definitely AG first imo. Would you rather drink beer out of a keg or GREAT beer out of a bottle?
I put together my AG gear really cheaply - under $200. Esky, pot from a camping/hardware store, couple of fittings and you're set. You can boil on your home stove in a pinch if it's not too big a batch.
I've had that for most of the year and only now putting together a keg setup. The kegs will be much more expensive - I'm looking at up to $350 for a basic setup with 2 kegs and picnic taps, and then you need a spare fridge!
My AG setup was the same, fairly cheap, already had Esky(put braid in, threaded pipe, tap, couple washers), got a $20 50ltr SS keggle(threaded pipe, washers, copper, ball valve), FIL had a 2 ring burner(works awesome), already had 9kg gas bottle and reg, silicone hose, etc etc... Probably cost me $150 to get set, works well... I think it helps if you are handy with stuff aswell and can do things yourself, some tooltards will just buy what they need and spend a small fortune..
Just ordered my keg gear today, 4 kegs, hose, dissconnects, PBW, starsan, lube, bronco tap, step clamps etc and cost $435... I already have a regulator($115) and a Celli Tap($115), then went to BOC and spent $83 on Gas Cylinder and 3 months rental..
So, without the Celli and just using a Bronco Tap, its cost $630 for my set-up plus a little.. Oh, also gotta get another dedicated Keg fridge(another $100) :beer:
Its up to you what you want to do and what your finances say you can do, ive been fortunate and basically got both things done within 2 months.. The thing I think about with getting set-up is that I save a **** load of money not buying commercial crap and no longer can stand drinking a beer at the pub club, plus you can always sell your setup either way for what you paid for it anyhow, there is always someone out there that doesnt want to do the hard work getting a set-up..
Cheers