Who to upgrade and which incursions crystal to buy?

Guillotine__

I am pushing for cav, and will do variant 3 and 4 once I hit level 45 to get another few 5* and some more rank up mats.
Would like to know who to upgrade from quake, guillotine and iBom. I will be able to take one of them to r4. I can quake and shake (can't heavy only) consistently (apart from silver centurion who always clips me for some reason) , but I feel health pools will get too high to quake. Was thinking of taking guillotine up, as I have the option to hit labyrinth for some more resources if she's at r5.

Additionally, I can buy one of the specialised incursion crystals for 5 star champs, or go for the basic 5 star. Was thinking of going for the domino/medusa crystal. Thought process is that although my roster is super small, I have the best unawakened science champs, and won't rank techs unless I pull ghost. Skill, mystic cosmic and mutant are weaknesses of my roster atm which id like to sort out. Plus medusa is a robot slaying beast.

Vendemiaire

Quake can help you clear V2 with iAbom. I suggest getting more champs before you go Cav.

Llessur

Guillotine 2099 is my MVP for the second half of Act 5 and the first half of act 6all you need to do is fire your sp3 when the defender is below 5% health and it is an insta kill unless it is someone that has a life saving effect like nick fury. also ending a fight with sp3 gives you a combo meter of 100 which makes you hit a lot harder. if you have trouble holding a combo parry heavy 5 times and you will have 5 combo sheilds which will save your from one hit each and also gives you a damage cap so hits wont hurt so bad. for power control you can spam sp1 and if you ended the last fight with a sp3 you can activate a prefight that steals power on the mediums just a warning doing this will reduce the amount of combo sheilds you can have. sp2 has an awesome heal reversal which is very useful. best of all she doesn't need her signature ability.