Your best bet will be to keep doing the rounds at thrift stores, meanwhile learning all that you can on these forums.
Right now the buy in and music on cassette is dirt cheap. You may need to lay back a while on the turntable, because those hit the radar of many, and the good ones go quick. Same with receiver, amps, speakers, etc.
As it stands with me right now, I think I only just recently broke the $100 mark on my system, and it's a rack system straight out of 1987. With the speakers refoamed and recapped, it's annoying neighbors once again.
Also feel free to explore the guided direction of the experts here too. They know how to play the game with the cards they are dealt, and they can help you do the same.