I'm 100% F2P and I got the 50k card last time. I conserve my e-gacha tickets. I had both N slayers and the alpha R. I had a BUNCH of radars saved from the previous gambit, and I ended up roughly neutral on those. I got a ton, and I used a ton.
This time, I had the beta R card from the Shards event (was alpha in Shards) and used 3 e-gacha tickets to get the new alpha R.
It CAN be done, but it's a shit ton of grinding. You have to work at it, and work hard.
Can this event be done? Maybe. It's going to depend on the frequency of the 5 step up kairo chances when you use radars. The clock is ticking pretty hard. It's not going to be easy, but it's not impossible either. Just save your e-gacha tickets for the event. I got one for the last perocolo and didn't use it. Slayers mean jack and squat to me during colosseum. I got an e-gacha during EG and another for 30 day login. Used one, saved one. I had 5 e-gacha tickets going into this event, and still have two. Depending on where I stand during phase 2, I may keep them or use one.
It's never impossible, but it's certainly harder.