You can get a compression gage w/ adapters at Harbor Freight for ~$15 on sale. They have quick release hoses which are also good for applying air pressure to hold valves up if you change the seals or springs.
Without a compression gage, the classic indication is a lot of blow-by. That is a routine test in my Mercedes diesels, which have noticeable blow-by even when good. Remove your PCV valve and see how much air is coming out of the hole in the valve cover. Use a back-light or hold a tissue paper. If nothing noticeable, your rings are probably OK. If it puffs the tissue paper noticeably, then bad.
If you need to save up some money, I once drove a Slant Six for a year with a bad cylinder by disabling that cylinder (to save fuel). I took the pushrods out and substituted a shorter copper rod with spring to hold the lifters down. Don't remove the lifters or you will affect oil flow to the others. That could give you better mileage, though the extra cylinder will give drag.