Help me decide the optimal order to learn spells

My only suggestion is that you specialize your mages. Instead of trying to do everything with one, you direct her towards one role. For example, in my last play through, Morrigan was set up for debuffing and crowd control. Wynne was healing and buffing. The PC was offense. Morrigan and Wynne were also set up to provide one half of all the good spell combos. For example, Morrigan and Wynne both had three electricty spells so the warden could quickly do Storm of the Century. They also both had Grease for much the same reason. Everyone had Blood Magic as a specialization with Wynne as a Spirit Healer, Morrigan as a Shapeshifter and the PC as an Arcane Warrior.

Hope that helps!

Generally, I like this build order the best but I tend to make the Warden a damage dealer rather than a supporter:

1 - Flame Blast, Winter's Grasp
2 - Flame Weapons
3 - Fireball
4 - Walking Bomb
5, Joining - Frost Weapons, Cone of Cold
6 - Vulnerability Hex
7 - Specialization
Tome - Death Syphon
8 - Virulent Walking Bomb

Has a lot to do with who you fight, and when you fight them. Gives you fire, ice and spirit damage right away for the Fade, then you can do the rest of the origin nearly completely with Fireball and Flame blast. Similarly, Korcari can be done with a ton of Fireballs. The one exception is Gazarath, who is resistant.

When you add CoC at the Joining, you have two good CC powers (Fireball and CoC) for Ishal and makes it easier to use Walking Bomb then it was in the Wilds. Vulnerability is just for bonus damage against the Ogre, but you can swap out Mind Blast there.

Level 7 spec in Lothering, I just grab Combat Magic or Blood Magic here. It really doesn't matter all that much. Combat Magic is very weak except as a way to equip armor, and Blood Magic is also somewhat tricky to use early but potentially pretty powerful. I almost never play SH on Warden, but Group Heal here works.

Now as to the spells in the OP. Obviously I am a big fire proponent, but conceivably you can swap out the Fire for the Electric tree in my order and do ok. I also don't generally bother to pick up the long cast elemental spells (Inferno, Blizzard, Tempest) since I don't like the cast time, nor do I cast Storm of the Century really. Out of any of that, I would just go Inferno, which deals similar DOT to Storm of the Century anyway, but I don't need it since I rely more on Fireballs and (Virulent) Walking Bombs as hammers.

Also a note on Entropy. I played an Entropy focused mage recently just for the hell of it. But honestly unless you want to do it just to do it, there is a lot of stuff in the tree that probably isn't worth worrying about outside of specific circumstances. For instance, Paralyze and Mass Paralysis are really not as good as Glyph of Paralysis and the Paralysis Explosion combo respectively. Since you have the glyph line, I would skip that first Entropy line entirely. Miasma is best left to melee Arcane Warrior. Weakness is weak, IMO.

The hexes are a good line though: the first two for bonus damage, and Misdirection will really hurt Revenants and some other elite melees, but isn't mandatory.

Drain Life is a nice one in Entropy. Heal while dealing spirit damage.

Now onto the Spirit Tree, if you want DPS it is the Bomb line which I already recommended. Although Spell Might is good for temporarily boosting spell power, the mana regen penalty is pretty large. I don't bother many times. However, if you are set on it, might as well pick up Mana Clash since you are already there (in the late teens anyway). If you don't want Mana Clash, I might consider skipping the whole line, since the first two spells are not that great.

Mind Blast line is pretty good, but I think the best two spells are right in the beginning. Mind Blast is good for stun, and Force Field is great for cheese tanking. Telekinetic Weapons has a nice AP bonus, but depending on party composition this may not even matter. Rogues will probably have good AP anyway, as will 2H warriors. Crushing Prison is honestly pretty mediocre, only single target damage and only CC on low tier enemies.

Speaking of which, Blood Wound is basically like Crushing Prison on steroids since it does basically the same thing to any living target in the AOE. Hence I would be more likely to drop TK weapons and CP for the next two skills in the Blood Magic tree.

As far as Creation and the heal / support spells, I would say where they fit is dependent on how much you want the Warden to be support vs how much the character is dps. I actually think the early part of the game is easier going all in on damage as player mage, but others may have their own opinions. Also somewhat depends on if you plan to actually use Blood Magic, and if it is really delayed until 14. Using Blood Sacrifice then Heal or Regen on that party member can net everyone health and is pretty efficient at good spell power.

With those disclaimers out of the way, here is how I would order most of that spell book:

1 - Lightning, Winter's Grasp
2 - Shock
3 - Frost Weapons
4 - Cone of Cold
5, Joining - Mind Blast, Heal
6 - Vulnerability Hex
7 - Spirit Healer / Group Heal
Tome - Force Field
8 - Revival*
9 - Glyph of Paralysis
10 - Glyph of Warding
11 - Glyph or Repulsion
12 - Lifeward*
13 - Rejuvenate
14 - Cleansing Aura*, Blood Mage
15 - Blood Magic
Tome - Blood Sacrifice
Tome - Blood Wound
16 - Regeneration
17 - Mass Rejuvenate
18 - Spell Wisp

*I used the levels you already had, but in actuality I would probably swap those for the rest of the Heal line in those spots since I think they are a little better. You can try to fit in the other primal spells after this.

The first tome I list is the one from Bodahn's first inventory, which you should be able to afford if you are relatively completionist and don't spend too much money early. The others can be purchased earlier than I listed them, if so just move up a slot.

If you don't want to use Blood Magic, I would drop the line and my suggestions there and go with the Fire spells or Walking Bomb line in place of them (although like I said I prefer both of those much earlier).