Here is my routine:

Subsequent attacks from the top 50 squads. there, both lv10, from worlds top first and second squad...
Thembad part is that my base always have 5k of contra to loose and the enemyes it offers me to attack have only 1-3k. The bullying boys can almost never be revenged becouse they are permanently online or under protection. So, for each attack to my base i need to make 3 attacks just to stay in the same 50k of contraband, but if i have to upgrade the droideka iand need 100k. when i reach 90k someone will attack me and take 9k. If i win the defense and another enemy comes five minutes later will be more 8,1k... and then i need to recover 17,1k wich means 8 common batles. So the game is clearly pushing me forward to buy protection not to loose my contraband or to complement in crystals (cash) the rest of the contraband and then wait 7...8... days upgrading the droideka, so it is pretty much a pay to win game... Not pay a little bit, is to pay a lot if you want to be with the big bases. And, if you want to unlock some goodies, and you are lv4-5, it is hard... so you upgrade the HQ...then it works but someday it gets harder and harder. You upgrade again but... Getting ultrachrome at some point starts to become more and more difficult and seems to stay with the big boys and the wallet warriors, making you start thinking if you should not spend a bit more too. If i'm attacked by assholes from the upper floor when they want, why can't i do the same? so that i can loot a base with 20k of contraband?
This kind of info you only discovers in the long run or trough other players...