I'd go with a mix of frontier civilian and cast off Army clothing.
Army coat and cavalry boots with a battered slouch hat, checkered shirt, dark red bandana, corduroy or wool striped pants, sldier's pants, drover's gloves, etc. Apache style mocs are good and can be comfortable. They often don't hols up well to extended use, though.
Straw hats were popular, but I don't recall seeing many sombreros. An Apache style head cloth/bandana would be good but doesn't protect you much from the sun.
Like the real scouts did, use what's available to you and get rid of anything that isn't useful. Avoid shiny and noisy items: buckles, badges, spurs, bright metal and bright colors.
Go with the Bowie. I like mine, but want a different sheath for it.