You should make the daily actions from the SFI-TO-DO page daily.
Also, you have to convert your TC into MRPs by participating into AUCTIONS.
And, finally, you should purchase something you need in a month from TripleClicks instead of purchasing from a store and get some VersaPoints.
Also, purchase TCredits packs from TripleClicks monthly so that you can have a sufficient quantity of TCredits.