make sure you have proper free play on the clutch rod under the dash, if it is too tight it will slip the clutch when engaged, simple inspection is all that is needed. Just make sure you have some freeplay in the clutch rod.

As mentioned above you could have a seized brake caliper piston, usually the rear, as the smells are similar on brakes and clutch material. Check all four hubs to see if they spin loosely when the wheel is off the ground, another simple check.

marble noise in neutral when the clutch is let out is usually a bad throwout bearing.