New long campaign player needs tips.

[Imp]

If you have halftracks why put the arty in them a couple of trucks left round the back just in case maybe but the trucks that moved your infantry up can go back & get them they are not front line vehicles.

MMGs I would go with more like Andy said depends on the map but they are your direct fire support. A double or 3 singles per company & often some can go to a position close to ATGs so can share transport.

FO risky move buying as a vehicle foot & a utility vehicle is safer, drive up & unload in cover.

HQ own transport ??? why if he needs it borrow a ride but only ever if you think its 99.9% safe sods law says it will get hit.

Add 2 SP Mrts per infantry Co as Andy suggested

If it was me would have bought a tank Co for command & control & deleted some, you have a lot of AT capability going against Polish hordes.
I would add jpz1 for France but for now possibly more infantry or add a platoon of Pioneers so they gain experience for quicker mine clearing might be the best option.
Depends on game size you want either way need to buy infantry with support points.

Points does not matter set larger than you need & buy what you want the AI will match it.