First of all, Why self chill Spark? 30% action speed makes mapping so much more fun. Most of people focus on 30% faster spell cast but for me 30% more movement speed is more important for mapping. Here is the tips I found.

1. Don't rely on reduce mana cost from flask: It just does not work even if you have tier 1 flask charge on crit mod. It never fully active especially on map boss. What you need to do is sacrifice damage from your skill tree and take reduced mana cost nodes, and buy jewels with 5% reduced mana cost. If your amulet has empty prefix, you can craft - mana cost. Also, It is very important you don't make Spark mana cost to zero because your Inspiration support won't trigger. If it is possible make mana cost to 1.
2. Crafting a wand can cost way more than you expected: the chance is around 1/4. It means you need to craft prefix cannot be changed 4 times in average, and also if you slam veiled chaos, It could brick your wand so you probably want Aisling instead.
3. Mageblood is not mandatory: You don't need Mageblood to enjoy all the fun.
4. Map is important for Spark: You can clear Crimson temple much faster than Strand because of more returning Sparks.
5. Craft Amulet and Shield by yourself to save currency: It is pretty easy and deterministic. You can craft them for half of the price buying it. Just search them in Youtube to learn how to craft them. However, Buy Spark glove from trade site. It is cheaper than crafting ATM.
6. The Pantheon Major God: You probably want Brine King. However, If your character captured Merveil already, You most likely need to make new one because it decrease your self chill effect by half(30% -> 15%)
7. Savage Hit does not trigger if you use Petrified Blood: I tested it and unless your chaos resistance is almost zero, It is not triggered by Forbidden Rite, so don't use Savage Response in you medium cluster jewel.
8. Chaos resistance: I capped my chaos resistance and the chill effect is 29%, so I recommend you to cap your chaos resistance. If you chaos resistance is lower than 40% you will see your life will goes down significantly every 4 seconds and will make your character can die very easily for a second.
9. Doedre's Elixir flask is really good for the build: You will feel the difference especially map boss and tough mobs. It is pretty cheap even if It is perfectly rolled. With Mageblood setup, You may want Progenesis instead.
10. Arcane Surge Support: It boost your damage a lot. Link it to Forbidden rite. However, You don't want to max the gem level because you can not make 100% up time. Adjust gem level and test by yourself to find the perfect gem level. For me it is level 10.
11. Get good corruption mods on your rings: You can find good corruption mod rings for decent price. increased cast speed and aura effects are very good.
12. Always care your low life: If you touch your skill tree, gem level and item, It can impact your low life. Always check reserved life after changing something. You can easily adjust the reserved life by adjusting gem level of precision or vitality which reserve your life. In my current setup, It is precision level 12
13. Map mods: This build does not like many map mods. I usually roll more than 50 maps using this keyword "regenera|less recove|of elemental|mum player"
14. This is an end game build for fun mapping: You need around 50div to start. Also, It is not a really good boss killer.
15. High Life regen is QoL: If you don't have high life regen, You don't take full advantage of Inquisitor passive Pious Path. I invested more on life regen over damage for budget build.

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​Here is my current POB

Budget Version: https://pastebin.com/wFZ4UP1j (fixed)

With Mageblood: https://pastebin.com/4aitSw9Y