Also using negative/boh boosters will help
I just stay at 2nd legacy because I have almost all my boosters gold and I don't wanna legacy anymore and I guess I'm a decent player
i rushed through the legacy levels. I play U3 5 hours a day of Co-op Arenas and Co-op Adventure. After playing 500 co-op levels im getting sick of this game . I stay away from TDM and Competitive. I am garbage at it. i do have 4,000 + kills in Comp but 5800 deaths .
Between U2 an U3 i have played them for 1300 hours combined
It requires 12,500,000 XP to reach rank 75 on Legacy 5. How fast you get there depends on how well you perform in matches and how many medals you earn in each match. Perform well consistently and play consistently and you can reach from 1 to 75 in under 2-3 weeks. So to answer your question, It all depends on you . Maybe 6,000,000 XP left? around that number I'm sure.