Questions about Mono white aggro/sideboarding against them

I've been running gruul ramp/ponza and been having some troubles against this matchup. Mainly cause of having to mulligan based on really bad hands. I want to know some good ways to fight against if you are at a disadvantage from the start/sideboarding. I usually bring in breath weapons, relics and deglamer. Board wipe, graveyard hate against their flashback cards and deglamer to counter journey to nowhere.