Mana stacking as a core archetype has been mostly figured out. It requires a lot of uniques to start, but they are all pretty cheap, and once you have them the build scales linearly. The strategy of stacking STR and INT with Shaper's Touch gives a very smooth progression path that can go on for basically forever. It's an archetype that you can start and end the league with.

Manaforged Arrow is a relatively new addition to the archetype. You can use it without stacking mana, but the strategy of using it while stacking has an even higher ceiling than regular mana stacking. It works by increasing the cost of your attacks through Indigon and then using that cost for a massive more multiplier through Manaforged Arrow Support and increased multiplier through Anomalous Mana Leech Support. This build, however, is widely considered not to be league start viable. The reason is pretty simple: alongside all the affixes you need to stack your mana and ES, you also need silly things like base damage, attack speed, crit/multi, extra arrows and accuracy. Getting all these things together on a level where the whole build feels good, requires a lot of investment.

However, there is a trick. The multipliers from Manaforged Arrow Support and Anomalous Mana Leech Support are generic. They work with every archetype they can link with, including DoT archetypes. You can use them with TR/CA and poison builds (through Voltaxic Rift), but I want to focus here on ignite.

PoB: https://pobb.in/hXdcBoPDa47l

This is an Elementalist build. You can start a Templar (if you don't want to relevel if/once you transition to hit based) by using a Stormfire ring. You halve your damage, but you gain a lot of ES. This Elementalist iteration costs about 2-3 div (with 1 div going to Anomalous Mana Leech Support) with prices from 1 week into the league. For that you get 8k ES and 11m (9m without EO) Guardian dps.

Ignite is great because it gets all its clear from proliferation. Multiple arrows and pierce are nice, but not necessary to get through a map. It also doesn't scale with attack speed, so that is another affix we don't need on gear. Crit is replaced by EO.

Ignite does present some challenges. The primary one is ramping our mana cost through Indigon. Even with our trigger bow skill having speed support links, we don't ramp that quickly. What helps here is Arcanist Brand. Another challenge is getting exposure. Wave of Conviction doesn't work for us because our base damage is mostly lightning and we can't get it on gloves either. The only realistic fix is a cluster notable. Our crit isn't that high and without pierce or multiple arrows we can't rely on multiple hits to proc EO. I don't expect it to be up all the time, but since we're constantly attacking to leech, it will be up sometimes.

TL;DR: use ignite to league start a Manaforged Arrow Stacker.