Actualy, sence not once person is in charge of what you should/shouldn't do, you should go ahead and put your costume together, the way you want to. I'm all for you using pads,etc. on your costume. I don't see whats wrong with using random stuff like that, sence it is a CUSTOM character, and isn't bound to a set of rules.
If you'd like to go a diffrent route for gauntlets, instead of buying Fett-esq. ones, you could do like a couple people have done, including myself, and use these -
http://www.thedentedhelmet.com/showthread.php?t=20105
And as recommended above, you might want to look into buying either a trashcan to cut your Mando armor out of, or some sintra, which is expanded PVC sheet to cut it out of. You can purchase sintra here -
www.usplastics.com
Sence your on a budget, I can see why you would want to opt. for a Rubies helmet, but realy, you can't go wrong with buying one of Sarg. Fang's mystery helmets. I know when I was first beggining, I was your age, and had a terrible time saving up money, but your costume will look better with the better quality of products you use. So I'd recommend trying to save up for one, but its up to you.
Do you have any ideas on what your costume's color scheme will be,etc.?