All about movement

Overview movement stars:
 

Cost of Movement stars

1-30-30
2-90-120
3-220-340
4-850-1190
5-1300-2490

Movement on other terrains (costs)
Plain: 3
Sea: 3
Plant: 4
Desert: 4
Forest: 5
Hill: 5
Mountain: 6

Max movement stars per division

Infantry - 4 stars
Tank - 5 stars
Artillery - 5 stars
Navy - 3 stars

Infantry (4 max, 3 recommended)

Medals expenses:
30 - Commando 2-->3
340 - Assault and light infantry 2-->3, Motorized infantry 4-->5
1190 - Commando 3-->4

You need to spend 340 medals to ensure you walk 5 hexes with motorized infantry.
Wouldn't go for the first, i always use MI instead of commando. And you need to spend 850 (1190 in total) medals to walk 4 hexes with commando instead of 3, i don't think that's worth it.

Tank (5 max, 4 recommended)

Medals expenses:
30 - Super Tank 2-->3
120 - Tank 3-->4
340 - Heavy Tank 3-->4, Armoured car 4-->5
1190 - Super tank 3-->4
2490 - Tank 4-->5

Even though the super tank upgrade sounds expensive, it's still the super tank aka the best unit in game. I would spend 850 medals to gain an extra hex on the best unit in game. The tank however, isn't worth the 1300 additional medals.

Artillery (5 max, 5 recommended)

Medals expenses:
30 - Field artillery 1-->2
120 - Rocket artillery 2-->3
340 - Battalion army 2-->3
1190 - Field artillery 2-->3
2490 - Rocket artillery 3-->4

In the beginning i would spend 120 medals to gain the extra movement for field artillery and rocket artillery. However in the end i would go till the max, since both field and rocket artillery are common used troops.

Navy (3 max, 3 recommended)

Medals expenses:
340 - all units +1

Do i need to say more?