Also if you don’t have access to power tools–
Home Depot and Lowes sell ‘handy panels–’ plywood cut to 2’x4’ size ready to carry home, as well as pegboard and other items. They also have circle panels pre-cut.
They will also cut some materials to size, either for free or for a modest fee.
You -can- cut 1/4" plywood with a utility knife! Just make sure you have something other than the good dining room table or the hardwood floor under it before you start!
Start with light strokes of the knife along a straight edge. Just apply enough pressure to cut the fibers. The knife does the work. Repeated strokes of the knife, with gently increasing pressure, will cut through the plywood relatively quickly.
Curves will be more of a challenge-- because you’re trying to make a straight knife blade follow a curve. Do it in little straight sections, and remove the unwanted wood in pieces. You may have to follow up with sandpaper of various grit sizes. You may want to invest in a finish sander as one of your first power tools!
Someone suggested Bondo. There’s also green modeler’s putty that is similar in function. And plastic wood! All used to fill in holes you made (or found) where you don’t want them!
Invest in a large breadboard. This can be used as a workbench if you don’t have one. Use it as backing when you’re drilling or sanding or painting. Ikea used to sell one with a lip that fits over the front of the counter you’re working on. This helps keep it from moving. It’s http://www.ikea.com/us/en/catalog/products/00309829/
Drill and bits
Sander and assorted sandpaper Sometimes a power sander can be your worst enemy, so be careful!
Nibbling tool - this can nibble holes in thin metal and plastic, following (relatively) complex contours
Hacksaw for cutting metal
Wood saw for cutting wood (duh)
Coping saw (ie jig saw) Jig saw also comes in power versions
Other hand saws as needed