One word of warning for your C64 hardware!!! Lots of the old c64 power supply bricks tend to fail with their advanced age, and when they do, they dump higher voltage onto a lot voltage rail in the c64 doing serious damage to the c64! If you post what power supply you have we can probably tell you if its one of the more risky ones. Alternatively, you can simply buy a modern one without this issue for about $60.
There are a few types of games that don't need a joystick (or paddles), like the RPG games Bards Tale or the Ultima series but, you're going to need a joystick to play most games. The good news is joysticks are also very cheap. A whole bunch of systems essentially used the same joystick config and connector. The same joystick that was used on the very popular Atari 2600 plugs right into the C64. I did a quick amazon search and found this brand new cheap compatible joystick for under $14 USD.
If you already have games on cassette, you can load and play those right now once you have your display (and joystick if required for the game). However, that will likely be a small collection, if you have any at all. You could go about buying a 5 1/4" disk drive, blank disks, and a USB PC interface cable for the disk drive, but that may be more than you want to buy right now. A cheaper solution is to buy a modern PC loadable cartridge like the Kungfu Flash 2 which can be had for about $35. You put the games on a microSD card, then put that microSD card in the Kungfu Flash cartridge, then plug the KF cart into the c64.