Exactly, that's where I am at. Level 3 summoners.
Now I'm doubting if I should sell the spare reward cards, because for some I almost have enough to go up another level, but that means I will have to level up my summoners too. I got the Fire oneup to level 4 (it's the cheapest one), but getting those commons up to 5 - or any other summoners up to 4, for all that matters - will be way too pricy.

Earlier this week, i was thinking about ending the experiment, and concluding that it is pretty doable to get up to bronze level (if you have some luck), but that it is almost impossible to get any higher.

I decided to go on, though. Who knows there's a gold foil Ruler Of The Seas waiting for me in my next set of reward cards, lol