The Tour Starter full set upgrade is both the most basic and most inexpensive at $7.92. I would also recommend a driver other than the Tour Starter driver to get a little more distance off the tee. The Pro tier R9 is 750 (?) credits I believe, so your initial investment is only $15. Test out the clubs with the default ball and see how things go. If the meter is too fast (particularly on the Driver) then purchase a 3-pack of GI-D balls (the ones with feel) and try that. The FEEL rating of the GI-D type balls slow the meter down and that makes it easier to hit more excellent shots.
I don't recommend any further upgrades yet, as some of the best players on this site still play with Tour Starter irons and/or wedges, so upgrading those right out of the gate is not really necessary. Learn the ins and outs of the game with this basic setup (and keep your total under $20 to boot) and then decide if you need to invest more later on down the road.