This seems a bit divided in strategy to me. Vehicles is generally a hard hitting aggro type deck that wants to barf out a bunch of efficiently costed beaters and then smash out a quick win before the opponents have a chance to stabilize and PWs is more about sticking walkers and then guarding them with board wipes and big blockers while they win the game for you. I get that your card pool sort of dictates what you do, but I think you could prolly split this into 2 lists that would both be a bit better at what they usually try to do. That said, without knowing what cards you have unlocked, its hard to make suggestions that aren't general.
I think for the Vehicles build, I'd cut
(except maybe as a splash for any Fatal Push/Unlicensed Disintegration you eventually pull and perhaps for recurring Scroungers).
These are the cards I'd consider keeping for the Vehicles aspect:
1 Toolcraft Exemplar
1 Shock
1 Topan Freeblade
2 Veteran Motorist
1 Scrapheap Scrounger
2 Smuggler's Copters
1 Reprisal
1 Ride Down
1 Declaration in Stone
1 Thalia, Heretic Cathar
1 Hanweir Garrison
1 Deepala, Pilot Exemplar
1 Skywhaler's shot
1 Borrowed Grace // possibly - depends on how often you cast it for value
1 Hungry Flames
1 Collective Effort
1 Kari Zev's Expertise
1 Akoam Firebird
2 Impetuous Devils
1 Gideon, Ally of Zendikar
Cards I'd look to add are any efficient 1-2 drop creatures (Expedition Envoy, Inventor's Apprentice, etc.), efficient PROACTIVE removal spells that can clear blockers before they block (Galvanic Bombardment, Shock, Fiery Impulse, etc.), and a few more vehicles like Renegade Freighter, Ovalchase (Fleetwheel when you get them), Harvester, and possibly the
D-card enchant that gives +3/+0, first strike, and autocrews vehicles, and a Start Your Engines or two as the Curve topper (don't bother with 5-drops).
For the Mardu Walkers deck, I'd be looking for defensive vehicles like Harvester and Heart of Kiran, along with a few good blockers like Gifted Aetherborn, lots of instant removal (Blessed Alliance is fine, but cards like Murder, Fatal Push, Harnessed Lightning, etc. are sort of what you are looking for), more walkers (2 ain't enough - you want Chandra, Torch and Liliana and prolly Sorin for that), and sweepers! Languish, Radiant Flames, Tragic Arrogance, Planar Outburst, etc. Back in EMN season, I had a madness Mardu PW deck that I really liked that used
Call the Bloodline with
Fiery Temper and some of the other madness spells from SOI to help with defense. Not sure how it would work out now, tho. Flying cars are all the rage these days.
GL, and brace yourself... I'm sure you are already aware, but set rotations are especially cruel to new players because all the ranks get reset and all the Spikes are playing their T1 decks in the single digit rankings. Next few weeks are gonna be especially hard.