make a list of the items you HAVE
make a list of the items you NEED
make a list of the items you WANT
make a list of the alternatives to the NEEDs and WANTs
make a list of the work that has to be DONE
make a list of the work in the order that it HAS TO BE done
for example, would you paint the engine bay before or after you install the engine? (don't laugh, people have done that! it's much easier to do it before obviously)
don't get ahead of yourself, stick to the plan. don't think "oh, I'll get the seats re-upholstered now and then store them in the garage until it's time to install". guess how I know about that one 26 yrs later? and they're still not installed (life got in the way, but not for lack of trying). those seats are still in my garage, covered/sealed in plastic, but a close inspection will show that there has been some environmental wear as well as drying out of the vinyl (seats for a convertible so have to be weatherproof). (and I won't even get into the 283 SBC I rebuilt in 1994, installed and ran for an hour or so, then had to pull back out, and has been sitting on an engine stand since then for the last 27 years)
example
because I didn't want to pay a lot of money for an axle upgrade, 2 yrs ago I decided to buy a used 7.5" axle (98% of gbodies have this), found a 3.42 rear pumpkin (also on this site last year), and purchased a cast differential cover from Summit and new pinion gear crush sleeve set.
then lightning struck. I literally bought an 8.5" axle off this site 3 days ago. those are almost as rare as hen's teeth, and in good shape no less. yet, this appeared and I managed to snag it for a great price and it should require no work. ok, what am I gonna do with the other stuff (axle, ring/pinion gear, crush sleeve, etc) that I'm now into for about $300-450? who's going to want to buy this?
Make a plan and stick to it as you do your work. If a special deal comes up then snag it, but don't prepare ahead of time like I did and waste money.