My first suppressor was a Sandman-S that I used on my .30 cal rifles, my 6.5g AR, and some .223 ARs. It works great on all of them. I picked up a YHM 556 for a deal I couldn't turn down, and I now run that on a .223 AR and it never comes off. I agree that you want to get one that is as versatile as possible for your first one. Because once you use it with one rifle, you're going to want to use it with the others too.
As far as the process, I did mine all as individual transfers. If doing individual, your first step is to go find a dealer in your area. You can buy from them, or buy from Silencer Shop and have it shipped to your local dealer. Silencer Shop is about as easy as you can get without going to a physical store. If you use one of their kiosks, it'll do your form and fingerprints for you there, and once in the system, you never have to do that again. Then pay your tax and submit your forms, and just forget about it for about a year. Once the stamp comes back, your dealer calls you and you go fill out a 4473 just like buying a gun, and then walk out with your can. My last can was processed using a Silencer Shop kiosk, and there were no problems at all doing it that way.
If doing as a trust, get that set up first, then the rest of the process is similar to an individual.