eventually, as I learn more, so how many watts of output power will I
need for most contacts? I don't want to start out undersized!



It depends.

For running around town talking through your local repeater on VHF/UHF,
somewhere in the range of 5 to 50 watts will do the job. It depends on the
heights of the respective antennas and their distance apart.

For HF communications, usually 100 watts is adequate. When conditions are
very good, considerably less will be needed. When conditions are marginal,
you may have to go up in power (limit is 1500 watts) or switch to CW. If
conditions are very bad, you may just have to go read a book as all the
power in the world won't help.

Dee D. Flint, N8UZE