Let's start from behind:
3) practice and have fun!
1) There some features which you cannot practice but have to pay for:
- Length, spin and a certain type of precision.
Buying clubs & balls is essential for these.
My suggestion would be to buy decent wedges (Ping or better) and a driver (perhaps the Pro driver) if not a full set of clubs. Irons, putter and balls can wait.
The higher level you come to, the better clubs will be available - plenty of temptations out there!
To get credits from playing you need better equipment - there are plenty of perfect players out there. If you don't want to spend money, look at "Get Credits" - "Earn free credits" in the top menu. Beware that free credits may cost a lot of your time!
2) The changes relevant for the game, length and green speed, come from advancement in the tiers. This comes from you playing better, a certain average is neccessary for each step. Explanation over there ==>