I'm new but I want to start working towards a Rohan force, let me know what you think:

Warband one
Eomer Knight of the pellenor mtd
3x royal guard mounted with throwing spear

Warband two
Grimbold
Banner bearer
7x helmingas
4x outriders on foot

Warband three
Erkenbrand mtd
2x son of eorl
1x rider of rohan
1x westfold redshield

500 points, 22 models, 8 might

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1401 models, 210 painted, only 1191 to go

I am tempted to say drop one Helminga and give the rest shields and upgrade that rider to a Red shield. It will make your men more survivable and won't effect your break point.

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Fight! Fight to the last man!

If this was to be our end then I would have them make SUCH AN END as to be worthy of remembrance

From what I've seen there are two ways of running helmingas, equip shields and go for the classic Rohan Shield wall.
The other is to equip axes and forget defence in favour of piercing strike.

Above all remember that the job of rohan infantry is either to hold ground that cavalry can't or to lock the enemy in place for cavalry to hit their vulnerable flanks.

In regard to the list I'd perhaps suggest drop one hero to add more riders as the mounted element needs a a decent number to hit hard, or even consider downgrading Knight of the Pellenor to marshall of the mark because in 500pts your going to need both heroes and numbers.
Hope this helps

yaa make a list full of helmingas and some cav :P

He can still get eomer knight of pellenor on foot(not as effective) but on charge gain S5 is still there :P