What would you suggest for a first reel to reel, 1/2 track or 1/4 track?
Half-track machines are primarily professional use. The extra tape width per track gives a slightly better S/N ratio and also helps reduce the chance of signal drop-out due to imperfections in the tape's oxide surface. The drawback is that any reel of tape on a half-track gives you only half the recording time.
Quarter-track machines are far more the rule in the home environment. As as others have noted, most commercially available prerecorded tapes are this format. I'd go with this format unless you have a specific reason to do otherwise. Note that the tapes recorded in quarter-track are not compatible with a half-track machine. However, a quarter-track machine will play a half-track tape.