It may be to early to ask, but does clan discount work for Invest?
The new mechanic Invest
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Clan discount and Invest are different things, and can be used together. So you can reduce GC by 2 thanks to clan discount, and then pay the Invest cost too.