The best/most popular strat items are Deep Route Specialist on offense and In The Zone on defense. You want 2 versions of each with +SPD and then a different second bold boost. If the bold boosts are the same, it is viewed as a duplicate item and will not stack. If 1 of the bold boosts is different, then the +SPD on each item stacks for +2 SPD total.

Here's a complete list of all the Rare Strategy Items so you can see all the possible combos:

https://www.mut.gg/news/mut-22-complete-strategy-item-list/

My Strat Items

Offense
1. Deep Route Specialist w/ +AWR and +SPD
2. Deep Route Specialist w/ +SPC and +SPD

Defense
1. In The Zone w/ +MCV and +SPD
2. In The Zone w/ +PUR and +SPD

Deep Route Specialist boosts SPD +2 for all of my wide receivers and In The Zone boosts SPD +2 for all of my defensive backs (corners AND safeties).

For a more detailed breakdown on how Strategy Items work and stack in MUT, read this:
https://www.mut.gg/news/mut-22-how-do-strategy-items-work/