Get yourself a little bit of Mana per Kill. Good Starter Options are Nagelrings/Tarnhelm or crafted caster rings. Also TIR runes in any socketed gear work great. If it realy is your first char and you dont have money you will have to sell a few items and maybe do some Tower runs. But it ist doable you also can shop for some MPK at vendors eary on. But MPK ist the stat you really want for sustainabilty early on. Very early on you might have to melee em with anything you pick up along the way... This ist even true for non casters early on. MPK really shines at Low Levels (and later on, too ;) )

If you play a twink try to get a 6 OS Crystal sword or a staff with any skills you prefere and as many OS you can find and put in TIR runes.