LeonDelBosque:
Since you can only get one, get the putter. You could keep it forever, whereas any driver you get now will likely be replaced; they get better as you level up, but many top players still use the Rossa. Plus, it's the club you use the most -- by far.
OK, my .02 again.
Have you seen a pattern here? Since about 50% of your shots will be made from less than 100 yds, most people are telling you to get better clubs for the short game.
I agree with the putter, and the Rossa is what I use. But I will not tell anyone what putter to buy. It's the club that is the most personal choice you will make. I would wait until you get to the Rossa's level, then rent the 3-4 that you feel would suit you best from the reviews. Then buy the one you like the best.
Then save your credits until you can get the G-20's, and buy them. They will last you until Legend, at that time you will have to decide if the faster meter on the R-11's are worth the trade off.
If you would like to try some balls, I used the 63 credit tour-s balls until I got my Burner 2.0 irons, then I needed balls that would slow the meter down. But even the 10 credit -s balls would help you control the spin on your wedges.
GL, on your quest.