You should go with a tank size you're comfortable with. You alone have to make that decision. You know how much space you have, what your financial situation is, how much effort you want to put into it. I don't think strangers can rightfully make the decision for you.
I've had a 38 gallon for years that I've been happy fooling with. It isn't hard to maintain and I don't go through nearly as much salt and other media as I would for a 125. To me, bigger tanks mean bigger money and a lot more work. Unless you have a fish room and can really do it right and automate as much as possible for water changes.
I'm upgrading to a 55 soon. Many will immediately say, why don't I go bigger. Well, a 4 ft tank will max out the space I have and it's all I want to deal with right now as far as my routine is concerned.
Then you get back into the money aspect of it. I'm going to DIY a sump/fuge, need a new skimmer, new light set up and canopy. Basically, another quick grand out the window for a minor upgrade. That's if I don't want anymore liverock or livestock.
Maybe someday I can get a new house, get my final large tank, do it right and be done with it. Right now isn't that day for me.
So it's up to you. There really isn't a right or wrong answer but the bigger the better, when it comes down to it.
