What Genie Should I Get As a Venomancer?

Which ever genie you can get for free.

There are 4 genies that you can get for free (you get one of the 4, random chance). They will all work fine.

Ona very important note.

They come in 4 basic colours.
Pink, White, Yellow and Green. So make sure, if you going to spend the money to buy one, that is does not clash with your clothes.
I use the pink one, that matches my purple/pinkish clothes.

If you going to grind, at least do it in style and do not clash your clothing and accessories.

I use a Longevity (green genie, dex for it's strong stat, magic for it's weak stat). Currently it's level 74 with 52/70 lucky points. It's stats are I think 5 str, 55 vit, 40 dex, and 43 mag. Some points are unspent as I haven't had a reason to spend them yet and I stopped spending affinity points as I have nothing to spend them on. The next goal is to take it to 58 dex, and gear for the final two points. Everything else will goto vit for additional energy I think with some possibly to mana regeneration, I haven't yet decided which would be more beneficial. Being on a PvE server this genie isn't geared towards PvP survival at all.

My skills are:
Eruption Fist - I use this all the time to split things, it's far more convenient than using a pet.

Tree of Protection 10 - This is an 80% heal, it's quite good if I need some HP, more coin efficient than healing potions, and is instant cast so if I'm low on mana I can take care of my HP as well. My most useful skill.

Extreme Poison 10 - This is for damage. Due to the 40 dex it's a 14% damage boost for 10 seconds, however it has multiplicative stacking with Amplify so I'm really getting a 16.8% boost out of it. When dex hits my goal of 60 it will be a 19.2% boost. This skill is expensive but worth it at times.

Relentless Courage 10 - This is a multipurpose skill, I primarily use it for the channeling speed. On some fights like Kong a few levels ago or Damned Gaurnob currently, I'm able to keep my pet up for awhile but eventually fall behind on heals. By using this skill for the additional 17% channeling (18% at 60 dex) I'm able to catch back up on healing and keep my pet alive. I can also use it with advanced spark eruption to get in one additional cast. The other reason I use this skill is for the run speed increase, which stacks with summers sprint. A 32% (33% eventually) run speed increase can be a life saver at times such as when my pet dies during an FB and I need to get away (happens about half the time on gaurnob). My one complaint about this skill is rank 10 is bugged, it should only cost 145 energy following the progression during other levels, however it costs 155 energy.

This may not be a good option for you, but it has worked out quite well for me. Also, I would suggest not leveling it up with you for the most part, until you can feed it spirit without slowing yourself down. The reason mine is the same level as me is because I stop to farm gear quite often, and because dying is highly possible when mindlessly farming, I routinely give all exp to my genie to prevent it from being lost by dying.