Guide to gaining inscription from 0.

On Hybrid, the inscription skill is especially useful to PVP mages because of the added bonus to the spells 'spell reflection' and 'protection'. With GM inscription, spell reflection is effective against 15 circles of magery - this means you can reflect 15 first circle spells, three fourth circle spells, two sixth circle spells, and so on. Protection becomes more effective by completely preventing the mage from becoming interupted. Note that you cannot have both spells in effect at the same time.

Gaining inscription takes some time and is fairly expensive, so it's best to begin raising it as your first skill, from 50. Expect to spend about ~$18k on reagents and about two days macroing.

Here's what you can do to save some money on reagents:
0-30: buy from vendor
30-50: lightning (mandrake/sulfurous ash)
50-65: energy bolt (night shade/black pearl)
65-80: flame strike (spiders silk/sulfurous ash)
80-100: summon elemental (bloodmoss/mandrake/spiders silk)

Vendors will buy back all of your scrolls, given they have available money, so you can recoup about half of the money you spent.

Bear in mind that this method is specifically designed with speed and initial cost in mind.If you want to recoup more gold, you would need to inscribe spells that avail a higher success rate (ie, at 55 skill, only do 4th-5th level scrolls). However it will take longer to reach 100 skill.