I picked up all the summon orbs except greater since they're usually annoying to get. Also picked up all the lesser power orbs since you want a ton of those to hone double strikes, retaliates and 2* elemental strikes. I picked up a few greater orbs but got fed up of doing those events.
The latest event gets you a ton of orbs. It's definitely worth going through even if you can only do normal. You probably won't get thundaja but you can pick up a lot of 3 and 4 star orbs pretty easily.
Focus on finishing the campaign though too. More stamina is always nice if for nothing else than the overnight fill-up. Odds are you'll have bigger gaps during the day too though. I believe max stamina is 100 currently which is 5 hours worth of resting.