The real consideration is, where are you going to fly.

If you have a big field (either your own or a club field, NOT a public park) then 30 or 50 size is an option.

If trying to get out to a suitable field is going to limit how much stick time you get (learning helis is all about practice), then you need a parkflier. That means something using 325mm blades or less... in other words, a T-Rex 450, mini-Titan e325, Dragonus 400, or something of that ilk.

Once you have the size sorted, it comes down to local experience and parts supply. Someone you can ask to look at it in person helps a lot, and parts supply is the #1 thing for a first serious heli. If you can't get parts quickly, you have downtime, you don't get the practice, you don't learn.