1) Get the clip. I didn't and I regret it. It's my only clipless pen and I'll never get used to it rolling around on the table.
2) Pay extra for the Conid tool. So you can easily clean and re-grease the piston.
3) Buy all the steel #6 nibs. They're about $9 each so you're not breaking the bank. That way when you get the pen there's less of a possibility of line-width disappointment because you'll have F, M and B at your disposal. Titanium and gold can be purchased later if you want to keep costs down. Or maybe steel is all the nib you'll ever need. I find Bock nibs to be pretty good.
This is good advice I think. I bought my Minimalistica with the F Ti nib and a M steel nib. I love the Ti nib and its bounce and feedback feel. I put in the steel nib the other day just to compare and it turned out to be a very nice nib. If that had been the only nib I got with the pen, I wouldn't have any regrets.