I love the 40 gallon breeder tanks because they are extra deep front to back compared to other small to medium size tanks. Let's you get more creative with decorating and planting. If space is an issue I would say look for a 40, plus a brand new 40 is only a little over 100$.
If space is not an issue I would say look for a 75 gallon. Only about 200$ and its big enough to open a lot of stocking options that would be unadvisable in a smaller tank. I have two 75s and a 40...love them both, but yeah, no matter what size you get you'll always want bigger!
Lots of people go for a 55 gallon, and its a fine tank, but the 75 is much better in my opinion because of the extra depth.
Whatever you choose, I would reccommend that you stay away from tall tanks because surface area is limited compared to volume of water, and your floorspace is likewise restricted. Tall tanks are visually striking, but for most fishkeepers floorspace and surface area are more important.
Good luck and welcome to the forum!