This is what i personally use there are other ways.
So basically you have two ways of upgrading a IG on 4U you can buy an IG and upgrade it to max (unusable whille it isnt maxed due to insect slow speed) or upgrade as you play.
This little guide will explain what i like to call burst upgrade, getting you IG maxed in one go, use it like a side note as its hard to remember all the things (at least for me :P).
For starters element nectars are basically useless as the insect damage is insignificant, to get the ultimate kinesect (effect extender) you have to get 96 in power, stamina and speed at the end of the upgrades.
what you will need per IG (all of them can be bought just rotate quests):
39 power+ nectars
47 speed+ nectars
18 stamina+ nectars
First feed it all the power nectars. yes all of them when it prompts you into picking a new kinesect obviously you pick the only one you can.
Remember this IG is useless untill you finish the process
Ok now for the speed nectar, you will want to feed you kinesect till your speed stat reaches 96, pretty easy.
Now you just feed all the 18 stamina nectars. You will notice that your kinesect will have 96, stamina 96 speed and about 114 power and will be level 10.
Now for the upgrade, you will want Bilbobrix! its the best kinesect

Now feed him the rest of the speed nectrars for the ultimate speed (SPEED IS IMPORTANT)
Enjoy your double extended buffs
Oh... wow... is that easy to make the Ultimate Kinsect? When I tried Insect Glaive in 4U I looked for a tutorial on the net and got all dizzy so I just went around feeding the kinsect random stuff xD