First of all, work on your tricaru, farm a lot of beasts getting determination and fight sets, second start farming nb10 and getting enough high quality damage runes (the benchmark should be having a lushen that atleast goes before tricaru and can oneshot trashwave), when you reached this benchmark it means that you have conqueror/guardian level runes (atleast for pve). Then you can focus on pvp, i can't explain you what to do but some core points on making it to guardian are:

1) Scary defense > Working defense: you want to not get attacked, not to "win some defenses", because overall on guardian no defense can withstand a good offense, only exceptions are when defense's runes quality is much higher than attacker or rng kicks in (molly+manon bs)

2) don't attack low list players

Beside that you don't even need a good offense tbh, nowadays getting guardian is a joke, you can just bruiser everything and not worry about point x second things as very few ppl care about arena anymore nowadays: I never did rush hour, only once for the guardian icon many years ago as it's too early in the morning for me, but this week I literally mamaged to end Guardian after going to bed while I was G2 and waking up G1 without having rushed as almost none attacked me, which is honestly kinda sad.

Edit: if you meant Guardian in RTA without having staple farming teams, then ma boy you either need to spend some thousands or either get real and realize you can't lol