Stone Concerns

I am F2P player, and am currently regretting using all 700 stones on the new beast gohan, he's at 55%.

I'm worried I wont have time now to collect at least 1k stones or 2k for the upcoming GDC celebration.

For some background I currently have a very good stack of charecters from the game as im a long time player however due to that I also have very limited sources for stone farms.

Would the best option for me be to just skip it and save for anni later as the units would return and I would have more characters I would need to get or should I spend what I have as either way I could try save between the 2 events or any other major upcoming events?