Dingus7:
Define upgrades. that answer was clear as mud
Bear in mind there is a comprehensive FAQ/Help that covers most subjects. My personal view is this could be clearly visible from the home page, not just a very small link at the bottom.or when you arrive on the forums page.
As for the OPs question Icon answered it - NO you do not need to spend money to play enjoyably, I played the first year here with only the free quipment/balls and yes it does make it harder to score well but is possible. Also bear in mind, the further tier advancement, the longer the tees and when you get to Masters Tier, the starters clubs just are not good enough.
My advice is to try and accumulate credits by surveys/videos etc see the GET CREDITS (top of the page) as better clubs do make the game easier to score better. Whether that makes the game more enjoyable is a personal matter.