If you have experience finishing drywall, you might consider having pros come in and hang it, you take it from there. Always get more than one estimate, but you should find that having a garage hung by a crew wont break the bank especially if you can furnish the materials, labor only on their part. You can insulate, finish the wallboard, paint, do the shelving, etc. If your are experienced elctrician, consider putting in extra receptacles, some up high in an area for a workbench, or in areas for shelving to charge those cordless batteries.

Ditto sierraeast. For me, drywall is the pain in the you-know-what; if it's done poorly, it will look bad forever. Everything else, before and after, can be DIY items. If your ceiling joists are on 24" centers, go with 5/8" drywall to avoid droop between joists. 5/8" on the walls is also stronger when mounting wall items to the drywall only - and more durable with kids running into it.