6to 8 ounces is good to start with. If you go over 16 ounces the heat generated will make it 'kick', or gel much sooner.
Use cheap plastic cups for measuring and mixing. Use once and trash them. You get small batches automatically, and no problems with contaminating fresh mixes with traces of older resin.
I like the translucent plastic cups. The clear ones are styrene and I avoid that. Not sure if it is just a prejudice of mine, or because the clear cups cost more.

If your epoxy mix is one part hardener to two parts of resin, pour about 2 ounces of water into one of your cups. Use a permanent marking pen to draw a line at the top of the fluid.

Stack that cup in another cup. Copy the line on the outside cup.
Remove the inner cup and cut a small hole in the outer cup. This hole goes on the line. Use this outer cup as a jig. Stick a fresh cup in the jig and poke your marking pen through the hole. You can now consistently mark as many cups as you need.
Put double the amount of water in another cup and repeat the process to make a jig for your other measuring cup.

If your cups are large enough, you can measure the resin, and still have enough room in the cup to add the hardener and stir things to mix them.
: Should I get the pumps? Will they pump too big of a batch?

You don't need the pumps, but they are a convenience. Don't rely on them to give you perfect ratios for your mixes. Double check with those disposable measuring/mixing cups.

Mix right in these disposable measuring cups. Dump the hardener into the resin and stir.

: Should I mess with a bubble roller, or depend on a squeegee?

Use both at different times. The roller is for wetting out the glass. The squeegee is for a very thin initial seal coat, and for filling the weave with later coats. A foam roller is also good for spreading the resin. Some people prefer one tool over another. They are chep. Try them all and see what works best for you.

Hope this helps

PGJ