It depends what you want, I have built a few.
If you want a SBK, it doesn't really matter a whole lot. I would probably start with one of the single engine ones.
If you want to scratch build, the FT plans or 13th squadron would be good. I really like the 13th squadron F6F.
**Warning, scratch building a full sized masters series plane can be tough, cutting out formers is tedious**
If you want to dip your toe into the MS stuff to see if it is for you, you could always start with one of the MS mini type planes.
I have built both zeros from 13th squadron and FT respectively, and neither of them are as complicated or time consuming as their larger counterparts. There is one thing that is tough about the 13th squadron zero, and that is getting that tail boom perfect.
I think my next MS build will probably be the Overstreet's P-51 design, unless they come out with the full sized P-40, then it will be that.
I probably need to crash some planes and make room in the hangar. I would like to see more civilian based MS builds. I am starting to design a Seneca right now, I am not sure whether it will be a full on master build, or some mix, or just a box plane.
If you're looking for a slower plane, and looking to scratch build, 13th Sq also has a Stuka, which looks fun. I think I would like one, but I also think I may get bored with it.
https://www.13thsquadron.com/ju-87-b-2-stuka-v2.html