There are several types of Marches boosters, but beware that if you activate several at the same time only the same type can be used! If you start a different type the previous booster is canceled. 

These boosters must be activated BEFORE you start any marching (100%, 150% and 200% marching speed-up).

Note: This only raises the troops you can send in one march - it will not magically give you more troops.

A boost that gives more troops in the march:

Troop enlargement by 25%

One type available, are active for 12h. Cost 5000 Gold.

Troop enlargement by 50%

Two variants, one that is valid for 15 minutes (given as reward, can't be bought) and one that is valid for 12h (10000 Gold).

Troop enlargement by 100%

One type, are active for 12h. Only available in package deals.

Troop enlargement by 150%

This type, are active for 10m.