Vaal pact and leech is so easy to get with attacks and its currently the best sustain mechanic. Easy access to dodge, better nodes. How to even sustain spell build?Spells don't need accuracy or a good weapon to perform. They purely require investment on the tree, a 5/6L and levels. Spell builds absolutely have access to dodge - there is a lot of generic physical, chaos and projectile scaling on the right of the tree. Just a remind, don't forget to from U4gm.com to buy poe currency, which is the best choice for path of exile orbs services on the market!
Selfcast.. not much. I've been pissed off about this ever since Piety was endgame. Spark totems back then mostly iirc, totems and whatever even now. Spells have shitty leech anyway, so the only advantage of selfcast is that it might have bit faster clear, maybe. Though, mines and traps are fine too. Almost like casting, except better. And they release shit like Shimmeron, just to make the point very clear. Self cast is not a supported playstyle, save oddities like RF+SR.
In my opinion, my build has cost me under 5ex total so far, but I've bought some pieces cheaper than they probably should have been.
2ex budget depends on current gear. You can get a decent shield and sceptre for under 2ex as a start. If youre running QOTF and its already linked, keep it for now. Try to find or craft a "places an additional mine" shaper helmet with life on it. Mines don't HAVE to be rocketed in helm for that, it's a global. If you get a good second support like spell damage, crit, hypothermia or inc air, better for you bit more expensive. Don't fall into the mine damage trap for other miner helmets, not worth. A tremor rod can work well for this build but it is absolutely going to feel a bit clunky. Part of that is movement skill limitations. I use shield charge and its just so much more fluid.
The other thing to run would be a couple CWDT setups. Detonate mines is a must for me, i also use phase run, summon ice golem, frostbite, convocation, and immortal call and another mana leech CWDT setup with bladefall and GC in it. Ice golem summon + convocation + Phase run dumps aggro to golem and let's me get away and reposition if I get hit.