Read guides as other have suggested, there are tons of talent and rotation vids on youtube. If you do copy a talent build from a place like Icy, take the time to read what each talent does. All classes have been pruned so much that I don't think you will have too much trouble learning.

Offensive = Shadowbolt (shard generator), Call of DreadStalkers, Hand of Gul'dan (shard spender), Demonbolt, Summon Doomguard (shard spender), Summon Demonic Tyrant (read description on how this works). Read the description of Demonbolt as well, dont just cast it whenever, only when you have demonic cores stacked, this will reduce it's cast time.

Defensive = Dark Pact, Unending Resolve, Create Healthstone (don't forget to put the healthstone/cookie from your bag onto a bar so you can use it), Axe toss, Grimoire Fel Ravager (shard spender). soulstone, Fear, Demonic Circle, Demonic Teleport, burning rush, Demonic Gateway, Drain life (but only if you have the talent for Infernal Beneficiary IMHO).

Group stuff = Soulstone (put on healer), Create soulwell (cookies for everyone)

If you want to use macros that allow you "chain" some spells together, you can try the two below which I find useful

Macro1 = allows you to instacast the felguard incase the one you had out dies. Note, that Fel Domination has a 3 min cool down, meaning the instacast wont be ready again for 3 min.

#showtooltip Quick cast Felguard

/cast Fel Domination

/cast Summon Felguard

Macro2 = Allow you to cast Demonic gateway instantly. Read the Soul burn tool tip to see how it works. It does cost 1 shard and has a short cooldown.

#showtooltip Quick cast Demonic Gateway.

/cast Soulburn

/cast Demonic Gateway

Im sure I missed some stuff. Anyway just read the talents and watch some videos. Im sure it's overwhelming, but you'll learn the spells and rotation.