Honestly there might not be a ton to do. I first started during Nero's event in summer and ultimately just decided to skip it since i really wasn't ready for the level of grinding required to get anywhere in an event. Focusing on looking through the saber and all sections of friends lists for really good units with event CE would be a good way to get an edge. I would suggest grinding expert rather than planet if you are done with lenses. Planet is the best place for transistors, but for vacuum tubes Expert is going to be the best place to grind at or below planet.
If you can get a team together that can beat Galaxy level its the best place for grinding tubes, but its difficulty is going to be a lot higher.
Lenses are actually best ground in the 25AP intermediate level (Aside from in star cluster, but having an archer as a boss makes that one a bit of a jump in difficulty)