Getting Mercury to Diamond

That's a fine build I'd just go Malice before DB, it gives more DPS and is cheaper.

Once you start getting good with landing ults, you can on one-shot someone by level 10. Land your ult (without too much distance past your target), auto attack twice, and use your 3 into Made You Look. That's your full on combo.

Use Special Delivery sparingly early unlees it's easy to get a pick if an enemy is near your tower line and there aren't any minions. Sparingly because it will leave you oom really quick. You can use it to interrupt things like Thor's 3, Fenrir's 3, Hun Batz 2, Bellona 2 etc. Just don't use it just to stop those if it will leave you in a bad position. Also, you're knockback immune during the duration of it even though it doesn't say so you can dash through Anhur's Impale or Disperse if timed right.

The hardest parts of Mercury is positioning, landing your 1, and landing your 4. You get pretty consistent with it, and it's easier to read enemy movement after practice since each will hit on a delay.

early crits are expensive and actually make your DPS overall lower during the mid game.

Also how about Soul Eater in the place of Asi ?