None of the spikes have a level or iLevel requirement to use. The limitation is on the blacksmithing level necessary to apply it. The felsteel spikes are just darned expensive for the increase over the thorium.

For casters I use the mystic spellthread. A pair of them put me back only 220g and adds a very large damage boost. You can also grab some old school mats and do the +power to gloves. There are no item limits for that.

For all classes you can do +100 health to chest and +sta to everything else.

For any class, Fiery is so OP it's not even funny. Heck, you could run a priest and melee/wand most of the mobs for the first 10 levels or so. Fiery procs about once per fight, so that a big pile of free damage.

Edit: I was thinking soulfrost/sunfire, but I just realized they are level 35 enchants now.