Think of Sweboz as the disiciplined barbarians. Their line units take a lot of beating before they break and have high density compared to say, Celtic units. Clubmen are useful for flanking, spearmen good line units, swordsmen are basically your elite. I wouldn't bother with the heavy swordsmen that much unless you need something to pin a phalanx.

Cavalry is sub par, their heavies match up with Celtic ones but the light cavalry is expensive and only decent for melee against other cav. I recommend lots of spearmen to form a sturdy line and some more as a mobile reserve to help deal against flanking cavalry. Also can use some Jugunthiz to skirmish and then sit behind your lines in loose formation to stop cavalry charges. Thier spears will deal with all but elite cav.

Use clubs to counter armor and swordsmen to flank. Wargozez to be the final hammer to break a shaken or wavering enemy line. I'd almost recommend using all infantry and just forget cavalry unless you have plenty of extra money.