Radio installation help!

I didn’t know if this was the right place to post this but it made sense to me! Have you all installed aftermarket radios in your car? And if so what installation kit did you use? There are ones I’ve seen that cost like 100-400 dollars called Retrosound, but that couldn’t be the only way! I’m not looking for something that looks retro, it doesn’t matter to me, this car is a daily so it doesn’t have to look like a show car, I just want the radio to fit, work and not look like crap (hanging half way out) Thanks!