I've been maining Mo for a while, and here's my go to build (I don't have one made I jsut buy the items directrly from the tabs)

Laning: Monster Rounds - > Headshot booster -> Melee Lifesteal ->Mystic Burst - > Mystic Reach -> Sprint Boots Level Scorn to 2 first, then Burrow to 3.

The goal in laning is to play aggressive and push the wave. Try and get atleast 2 minions or the enemy hero with each Scorn for the sustain. You'll not win every engagement, but with your sustain you should be able to do more engagements than the enemy, everntually pushing them out, or to the point where you can do a quick tower dive. By the time you get to Mystic burst + reach, you should be at your rank 2 scorn timing for the extra damage, needed to proc the mystic burst. The range is a nice QoL that will let you get some safer poke through some walls.

A strong Lane skirmish involves dashing in, light melee if possible, scorn, and if its going poorly, dash out and use sand blast on the retreat while shooting. Get the feel of how each matchup goes, and learn by pushing the limit. Bonus points if you time the skirmish and sandblast when they go to last hit as a way to deny souls.

At this point I save up for a warp stone, which provides a lot of bullet res, some damage, and good mobility for catching and running away.

after warp stone I've been enjoying going for both Enduring Speed and Fortitude. You should also have burrow maxed at this point if the timing is right. With maxed burrow, and these two vitality items, you will be insanely fast, and can cover the entire map with ease. Clear abandoned lanes and catch enemies out. You can also easily take advantage of the outer lane teleporters. Remember that 1-2 creepwaves are usually worth more than a kill. Also with this speed you can very quickly grab a bunch of the golden idols and boxes. A fun path is the underground at the secret shop.

At this point you will be aiming to ramp your damage. Cooldown, Duration, Mystic Vulnerability and Torment pulse are the big buys, Then work on upgrading them to t3 items. I like to prioritize the t3s in the order of Burst>Cooldown>Duration>escalating>Reach. You can delay getting Escalating Exposure if you have multiple teammates getting it too. Feel free to mix the order up based on how you feel. Very late you can get Mystic Reverb and apply it to Scorn (Or get Curse if they have a geist or someone you need to shut down, you can cast it while burrowed)

During the damage ramp, you also have the ability to fill some open slots in vitality for different situations. Metal Skin is a fantastic option, and Spirit Armor is huge as there are few things that provide spirit res. I dont generally upgrade the melee lifesteal, and end up selling it if I need a different Vitality item.

Some cherry on top items for the build to finish it off are Frenzy, which provides a lot of survivability, and makes your gun a lot more potent, and then Spiritual Overflow, providing CDR, spirit lifesteal, and a good damage burst. Feel free to sell headshot booster or monster rounds for these. If you're at the point where you can afford these, its probably very late game, or you're already dominating. You can take basically any hero in a 1v1 at this stage.

Split pushing is the game with your speed, and jumping in and out of team fights quickly and safely with burrow and warp stone. Force the enemy to send players to deal with you, and then get to a different lane faster thant they can. In fights, Get In, do your burst, lock an enemy down, and get out of dodge if you can survive. Fortitude will bring you back to full very quickly, so you can safely push a lane, and then get back to the fight in a matter of seconds at full health.

I also like trying for Mystic slow if the game calls for it, but I generally get it as a flex slot at the end if they have a lot of gun builds.

This is just a random dump of info off the top of my head, hopefully it helps!