1) There is no single bad event eydo. If you don't need them - it's 750 orbs from event. Keyser costs 10k, t4 soul - 3k so you need a lot of them. + sometimes you may get Anubis/Magna/140% so you need a single element grid to maximize a performance so any eydo of chosen element is good.
2) gems quests are almost never needed if your account isn't super new, you will get more then enough if you are not super space whale.
3) forget about t3/t4 stars if you don't need them right now, drop rate will be much more soon
4) i highly recommend to focus on t2 idea cores and fangs- they will be your main problem next year.