How much max mana pool size do you get by wave 100 in Gemcraft Labyrinth?

By wave 100 your mana pool should be around 250-300k

What you need to do is build a mana farm at the beginning of the level. If there is more than 1 entrance for monsters put it just after their paths converge.

I typically use a straight section of path and set up 3 traps with lime/orange gems that are surrounded by amplifiers on each side (6 total) with L/O gems. The trap gems should be 2-4 grades higher than the amplifiers.

This setup will get you mana at an extremely high rate as the mana gain is also applied to the multiple hits lime gives you. Because you gain mana so fast you can upgrade extremely quickly. I can usually get to level 12 or 13 for all gems by wave 70 or so. You can extend the mana farm as far as you want but this small one will get the job done, cost very little (comparatively), and most laptops will struggle to run smoothly even with just these 3.

Protip: At this point you should shift-click the extend mana pool spell. It will automatically cast when the mana bar fills and extend your pool at the fastest possible rate. If you've never done mana farming like this you will be blown away by how quickly the bar fills.

3 level 13 gems surrounded by 6 level 13 amplifiers will be able to take you to about wave 190 before anything is able to get through. So you have between wave 70 and wave 190 to build a killer gem towards the end of your path uninterrupted. You can upgrade your mana farm along the way but you'll see rapidly diminishing returns. After wave 220 or so it doesn't matter how high level the gems in the traps are, monsters will start to get through.

A level 21 gem surrounded by 8 level 20 gems will be able to kill monsters faster than they enter the field, even at max HP. Then just ctrl+click the waves and sit back. You'll get between 1-5 million XP depending on the map and the number of amulets you earn.

You don't have to upgrade. Combining increases power too.

Suppose that your max mana pool is around 100000. Then create gems who whorth 90000 and combine them to get a gems that have a greater value than 100000.

Honestly When I play, I play with a combo of lime, orange and yellow. I play using traps and amplifiers. I don't do the tradition mana farm but my main gem ( the only one in a trap) is both to farm and to kill.

If you need mana to upgrade I suggest this to you: use a combo of lvl 1 orange and yellow gems, lvl 2 lime, lvl 3 yellow, lvl 4 orange, lvl 5 yellow and lvl 6 orange gems to start off. Combine these to get a lvl 7 gem, and put it in a trap. Duplicate it and put that gem in an adjacent amplifier. set auto mana pool increase before the rounds start. Gem bomb the first couple of waves with 1-3 lvl 1 gems. Duplicate your gems and fill the amplifiers around your trap then upgrade your main gem in the trap. by doing this I have over 1 million mana before lvl 30.

I am lazy so I am going to stop here, but I will say I've had my fun starting this way getting up to a lvl 47 gem and a mana pool big enough to duplicate lvl 36 gems. Have fun :) if you need more instruction sorry but you should be able to figure the rest out after you are told how to start.

One more note for those doing endurance, a lvl 32 gem in a tower surrounded by 8 amplifiers at lvl 28 should get you through all 1337 waves. At least with my points used how they are it is good enough to let it just sit and finish while you are away.