Bit of advice from my side:
1. Whoever you are playing for, don't build regiments: build only brigade/division formations. The reason is, there are only 9 slots for units per division, in each of those 9 slots you could fit a brigade of four regiments or just one regiment. Aim for large divisions: since of the poor parts of the game engine is if an attacking division is destroyed, the whole stack withdraws from battle. Plus on the battlefield, it seems to not matter the true size of the unit: division, regiment or brigade, in battle they all take one deployment slot. Though, this does not apply to artillery and special units(armored cars, tanks, tachankas, elite regiments etc.)
2. Don't use your army commander as a commander of a stack. One of the major reasons why I lost one game was because the stack under command of Denikin didn't attack when it was supposed to. Though you could use an army commander stack as support to your frontline corps(Marching to the Sound of Guns, when an engaged corps calls upon nearby corps and the mother army(if close enough) to help).
3. Cavalry though has low fire values, may be extremely effective for deep raids behind the frontline.It also is very effective in the winter(when time to hand-to-hand combat is decreased).
4. Have little hope on exhausting the enemy by cutting supply lines. It is very tough and time-consuming.
5. Division formation:
http://www.ageod-forum.com/showthread.php?23976-Division-composition-that-you-use
There was also another similar thread, which I can't find for some reason.