I think it's worth it. You'll never regret having those two centies. Kinda like you will never regret saving your 500 life crystals a month for the rainbow skill bloom on Nutaku.

One thing to keep in mind, though, is you want to try to keep a buffer of 250(00) FGs, in case they have the gacha event where you get a guaranteed rainbow if you make 55 pulls. They've done this twice in the last year.