There was a thread about this before (
http://www.eqmagetower.com/forums/viewtopic.php?f=6&t=547) but I think that was pre-underfoot. I'll throw my general spell lineup here (this is for 12 gems):
1 - Bolt
2 - Fickle
3 - Thaumatize
4 - Pet rune
5 - Brimstone skin
6 - Pet heal
7 - Pet Promised Heal
8 - Iceflame tenement
9 - RS
10 - Burnout
11 - Burning Brimbody
12 - Twincast
Replace 1 and 2 with ATA spells when fighting valid targets for those spells exclusively. In a mixed bunch I just stick with the fire spells. Burnout and iceflame are my two swappable spells gems, which I trade out for buffs or summon items I need at the time. This is really my soloing lineup, but I don't change it around that much for grouping (maybe drop the heals for summon ice shard so I can summon those on GoM procs when the current mob is low on health).
Something that can easily save you a spell gem is getting the AA malo. It's also harder to resist than regular malo, so once you get it you'll almost never load regular malo again (except maybe on raids).
I do wonder why you have so many different DD spells up. I understand that's what we do, but I'd like to comment on your spell choices real quick:
Torrid sands - not a spell I ever find terribly useful. I don't recall it being particularly mana efficient (I think quite the opposite actually), or making a very big boom. It's fast casting, but I think that's all it has going for it. You'd probably be better served with bolt loaded since it hits harder and is more mana efficient. TS is ok for runners, but isn't enough to take one down much unless they're really weak.
Shock of Discordant Steel - Unless you're fighting really fire resistant mobs or are specialized in conjuration I wouldn't load this. Not that it's a bad spell if conj specced, but I personally don't use it much.
Deluge of Thunderbolts - If you're fighting 2+ mobs at once and your tank can keep aggro on both, our rain spells are great. They're very mana efficient on 2+ targets. Unlike shock of steel this is a magic based evocation spell, so good if you're evo specced and fighting fire resistant stuff. Still, I'd think the determining factor in using this is if your group is pulling 2+ mobs at a time and your tank can keep aggro on both. If so, don't just use this, use rain of molten scoria as well. Otherwise I'd stick with a single target nuke.
Fickle Blaze - hands down one of our best spells. Yes, this should always have a home in your spell lineup unless you're fighting things you can use ATA on. Even then it's still not be a bad idea.
Other spells you have up:
Surge of Thaumacreation: I never use this. I have it, but I don't think I've ever even loaded it. That said I'm not in much of a position to criticize it since I've never used it. I understand most mages don't like it, but if you do, more power to you.
Chaotic boon: Unlike most mages I really like this spell, but only for soloing. If I'm not using my merc I find this is a fairly mana-efficient heal for my pet. Pop it and nuke away and hope it procs enough to keep my pet up. If it's not keeping up I drop the occasional promised heal as well. In a group though I don't see much use, particularly since you have an SK to tank for you most of the time.
Ravenous Flames: Might work well for you since you're usually grouped and have a valid player tank to cast it on. I don't use it for the long recast, but if it works for you, stick to it.
After all of this, I'd like to point out this is just my opinion. Your mileage may vary, and if you enjoy some of the spells you're using, great, keep using them. I just tend to stick with evocation spells since that's my spec, and either ATA or fire spells most of the time.