Well, I heard Arc is a good building to have, but only 2 guildmates have the arc, and it's impossible to get any contribution rewards as other people pump hunderds of points in there. I try with polishing/motivating specific buildings but I still have 0 Arc BP's
Be brutal with your friends list. Take the bottom 10 (by score or by tablecloth) and get rid of them. Then hunt around (using ranking, friends of top guild mates, friends of top friends, etc.) for players with The Arc. Apply to be friends with them.
You must have a top tablecloth for them to agree: few will bother with you if you don't have at least a Royal. You will get about a 50% sucess rate, so after a couple of days, remove any applications and apply to a new set. Then take another bottom 10 off y9ur friends list and repeat.
With 20 players on your friends list with The Arc, drop 1 FP on to each of them and keep a close lookout for opportunities. If you make sure all those new 'friends' players are in AF, even just the aiding the aiding will bring some results. Really, blueprints for The Arc are so abundant that once you get going, you'll wonder where the rain of Arc blueprints comes from.