Focus on smooth surfaces. Any texture will make you go slower and more gently. What instead you should do is get something short and girthy with perhaps a large base or handle. Something you can easily grip and use to thrust. Don't count on suction cups but they can be nice, doesn't seem like most are any good for what you could eventually learn to do.
Focus on something that you can adapt to rather than something to immediately graduate from. The slim beginners butt plugs are essentially worthless unless you can't get your pinky up your ass. In that case, I don't know how you even would poop.
Don't spend too much to fast, and don't get the cheapest thing from a local store or amazon. Instead, expect to spend up to 60 dollars
I've heard a lot of good things about the nofrilldo>>9212376 knows what's up pretty well.
Also, things likehttps://www.lovehoney.com/product.cfm?p=30703
Good luck, whatever you spend on the toy, you'll spend a lot more on lube so don't skimp. Get something water based and thick/viscous. Sassy by Sliquid is pretty good. Make sure you aren't allergic or something neither cause you don't wanna end up with an inflamed asshole.
Don't go cheap, don't go fast, be safe and good luck!