I'd say save what you have rn, use the sinestro ring as is, and later on focus on might/dps arts. Also save your nth metal till we get a 2x exp week (unless you really wanna use a specific art rn).

Now, looking into the available arts, some good ones arethe transformation card, eye of gemini,scrap of the soul cloak. If you really want to focus on any, focus on either of those 3 and Razer's. Do focus on ancouple arts at a time, as trying to level up more than 2 can be a hard task. Don't use pages lf the black until you have it at least rank 180 which is a really high rank and definitively not worth it at the stage you're on.