I would advise against that.
Here is why... You are not sure what size tank you are going to get (I would suggest at minimum 55g) If you run around now, buying a ton of equipment and then get a tank somewhere that the equipment doesn't work with, you will end up replacing it all.
I seriously advise making a firm decision on what tank you are going to go with and THEN start getting equipment to build that tank.
An RODI would be a good starting piece to get now. You don't need a specific tank size to get that. Also a couple brute cans for your water station would be good and a strong pump for your SW mixing can. I wouldn't get any other equipment other than that at this point.
Just my $0.02
