Seems like there's a pretty set ratio:
- Tier 1: earn .56 miles/$
- Tier 2: earn .64 miles/$
- Tier 3: earn .74 miles/$
- Tier 4: earn .89 miles/$
- Tier 5: earn 1.11 miles/$

All my credit cards are with Chase, and I put about 40-60% spend on my UA cards. If I stick with that pattern, I should hit the first tier pretty easily. I think I'd hit Tier 4 if I put 100% of my spend on just the UA Quest card. It'd hit Tier 5 if I did that and spent in total 20% more than I usually do.