If you're playing on PC, here's a list of mods I highly recommend:
Free Remnant Decryption Keys (1000x)
Road Rage (increased Nomad collision damage to enemies)
Materials for Sale (all crafting materials can be bought on the Tempest for free)
General Augs Rebalanced (full disclosure: I made this mod - sets a wide variety of augments to give 10% bonuses to weapons/gear)
Weight Cooldown Bonus (brings back ME3's less weight = faster cooldowns mechanic)
Hyper Mobility (better sprint speed, better jump height & distance, might get you stuck on invisible geometry)
Squadmates Damage (buff to squadmate stats so they're less useless)
No Profile Switching Cooldown (switching profiles doesn't cause all abilities to cooldown)
Shut Up SAM (Reduces SAM chatter about environmental hazards)
Cheap Research (Reduces research costs by 75-80%}
Research No Level Requirements (Actually build the highest tier stuff without going into New Game Plus or tons of grinding)
Shorter Landing and Departure Cinematics (Cuts most of these cutscenes down to sub-10 seconds)
Increased Weapon Range
Faster Kadara Doors
Nomad Top Speed Increase (Now it peaks at 200 km/h)
Ultimate Camera FOV mod
DS4 Buttons
Tools you should have:
MEA Recovery Tool (let's you revert changes if modding causes problems)
Frosty Mod Manager (lets you run mods in a nice UI, remember to double click the mods on the list to the left)
MEAExplorer Ansel DLLs (download them & stick them in the MEA game folder so the mods will actually work)
Edit: You don't need the DLLs with Frosty Mod Manager.