My son has a program he follows, set up by his coach. Depending on the day, it is medball throws, weighted balls, long toss, bullpens. He lifts most days and does bands. We have a mound and a net and he throws into the net except for bullpen days, when his pitching coach meets him with his catcher.
You can do the driveline off season program without much equipment (other than a couple of their balls and the trampoline). It is a good way to keep the arm in shape and maybe get some gains.