Talk:Porsche 911 RSR Championship (v5.0.5)/@comment-108.59.48.4-20170217155247/@comment-26829117-20170217192743

I take it you haven't discovered the Upgrades Strategy For 100% Completion page then? It attempts to calculate the cheapest way to get to 100% in the career series.

If you have a look at the GTE-Pro: Chevrolet and Porsche section you will see that you need to upgrade both cars to PR 89 to complete the series and one car to PR 90 with the Corvette being the cheaper option. So the total gold cost for you to complete this series is:
 * Porsche upgrade to PR 89 - 667
 * Corvette upgrade to PR 89 - 667
 * Corvette upgrade to PR 90 - 170 (Porsche is 180)

Therefore the minimum upgrade cost of this series is 667+667+170 = 1,504 for an 80 reward giving a margin of 1424.

I'm assuming from your comments that you didn't win the Corvette so you have to add 520 if you buy it in the showcase.

My advice would be to go as far as you can with current upgrades and without triggering the showcase discount. Save your gold, build up a reserve, so you can take advantage of car and upgrade sales if and when they come along.