Hi! Sounds like you've got a healthy number of systems already, we should certainly be able to get at least one of them "up to speed" for you.

If you just want to play games and you don't want to spend much money on the hardware, you've got pretty much two options, as you already surmised:
A Gotek or HxC-style floppy replacement: exactly what it sounds like. Typically replaces the internal floppy drive with a board that allows you to interface to a USB flash drive or SD card. You'd plug that flash drive or card into your PC, load it up with ".adf" files (Amiga disk images), and play-away. Logic in the unit is smart enough that for multi-floppy games, there's usually some option (such as a button on the device or a keypress on the system) that triggers it to "switch disks". This typically requires very little hardware expansion beyond the unit itself and there are many options available.
WHDLoad: my preferred solution, especially if you have an upgraded system. WHDLoad uses "install" packages to make many older programs compatible with more modern software. This would allow you to, for example, boot your Amiga to Workbench, double-click a game icon to play it, then press a quit key (usually F10) to return back to Workbench after you're done playing. WHDLoad is probably the more "sophisticated" of the two options, games load faster (because they're not relying on the floppy drive interface), and usually requires your Amiga to have at least a small amount of fast memory expansion. (the target system is something along the lines of an A1200 + one of the new ACA accelerators).
Sorry we can't point you directly to links for Amiga games to download, the copyright police here won't let us, but Google is your friend. The main WHDLoad support page (contains installers, but no full games) is here:
http://whdload.de/ And here's a cheap link (among many) where you could buy a Gotek from a reputable Amiga vendor:
http://amigastore.eu/en/323-usb-floppy-emulator-gotek.htmlGood luck, happy gaming, and all that.
