If you have Alexis levelled up then go back to Cyber Angels. Summon Benten (preferably with Idaten as tribute) and then battle any level 20 opponent. They keep putting their monster in defense mode and can't really defeat a 2800 ATK monster. Benten then does effect damage equal to defense of destroyed monsters. You should reach 5000 in two successful matches using R rarity cards only
Anoymous
Revolver