As my front line infantry, I go with 2Inf+2Art. They are powerful and modular, meaning I can divide it in two if necessary into two divisions of Inf+Art. Those mini divisions are useful as garrisons for ports and such. Then if the front approaches, two mini-divisions can be joined as a front line division. When superior firepower comes around, I'll throw in an AT brigade if I'm on defense. When on offense, I start thinking corps. Each infantry corps will be comprised of four divisions. The divisions will each detach their AT's and form a new fifth division of Inf+4AT. The four 2Inf+2Art divisions attack as usual, and the fifth tank killer division follows ready to ruin the day of any panzer commander thinking about a counter attack.
My mobile divisions are usually, 2Mot+2TD, and then Mech. Sometimes I don't bother building tanks.