I would honestly suggest saving your NX for a gun you like using and is also on sale.
Between the XM8 and the L85A1, the XM8 is more "noob friendly" because of it's low recoil, portability, and fire rate. Though, they are both great guns in my opinion. However, the XM8 can not be purchased for a permanent duration, so you will have to wait for a sale, or until Nexon sells it for perm.