Radio Controlled

I fly FPV drones mostly.

I order often from: getfpv.com, readymaderc.com, and racedayquads.com. I've also ordered from quite a few other sites but try to pay close attention to delivery estimates If I want something quickly.

For the most part there is pretty good interoperability on parts. Transmitters will speak one or more protocol, make sure to get compatible receivers there. Video systems are similar, analogue hardware is fairly interoperable, but if you get a digital video system you need corresponding video transmitter/camera. Not all motors are equal but even pretty cheap motors can get the job done. From a power standpoint you want to make sure any speed controllers you're using are reasonably matched to your motors.

Ardupilot is probably best for automated systems, waypoint missions, position hold, or otherwise photography platform like activates. Ardupilot also gets extra points for being versatile planes/drone/boats, etc from one controller. If you want to actually pilot a performance drone you'd probably want to lean more toward betaflight and its forks/competitors.

When it comes to aircraft, if you're new, expect to crash and break them. They can be fairly durable but really when I buy something I'm thinking about it's flight characteristics and features more than it's cost. $20 isn't going to make a big difference here. Transmitters and Video equipment are much better investment opportunities. A nice transmitter with quality gimbals can last a decade. Quality FPV goggles will last also and improve QoL. These are where you want to invest.

That said a really cheap transmitter and some crappy box goggles are better than not flying at all.

Planes differ from drones in that they can be flown without a flight controller (direct PWM to servos). Though a more purpose built (fixed wing) flight controllers can make the job a bunch easier by trying to help hold orientation. I'm pretty new at the whole fixed wing thing.

A blimp sounds like a great time, on a really still day, or in a gymnasium or something. I've also seen RC paramotors that look like they might be groovy!