Take lucky. If you get crit you're probably dead. With high AC, you're not likely to get hit much but a natural 20 always hits and hits hard. 5% chance to die isn't great! Lucky gives you a get out of jail free card. It has plenty of other uses too but the main one will be to avoid getting critically hit.
Important spells include shield, mage armor, Shadow blade or haste, find familiar, mirror image, Misty step (to get in range or out if range), absorb elements, and pretty much anything else that helps you stay alive or uses something other than your action. I also really like polymorph for when you're low on health. When you cast polymorph, you take on the health of the thing you polymorph into. It's better than any heal!
You might also want to grab either war caster or resilient Constitution to help maintain concentration on spells. You get a bonus on the saves from your intelligence so that helps. Lucky can also be used on concentration checks or to prevent the damage. You won't need to get way caster or resilient Constitution early. You'll likely want to Max intelligence and grab lucky first.
Consider your party, if they are mostly melee you will hopefully avoid drawing all the opposition attacks. Consider whether you are attempting to use the subclass for defence, or to provide you with a real melee option. If melee then look at making booming blade and/or greenflame blade part of your arsenal. Contemplate if taking a level of fighter before you switch to wizard might be better for you. (con saves for concentration, second wind and a fighting style. A downside if you really want to be an elf bladesinger is armour being incompatible with your subclass armour bonus)
Your first level spells will likely be expended on shield and mage armour to increase your life expectancy, Due to this false life is a choice that will be difficult to accept (especially considering the duration and limited effect) Bracers of armor (magic item) should be drooled over and hugged like gollum would a ring.
Second level spells are trickier, choose wisely, too much 'how to avoid dying' ink in your spell book will prevent you from preparing to kill people with magic. An obvious choice is magic weapon, if your in a low magic game especially.
Regarding melee, you will never have the hitpoints to shrug off damage, you wont be able to heal that damage with your class either. So play smart. Dont charge in first, dont expose yourself to mass ranged attacks or melee attacks. Do try to eliminate targets one at a time. Do use spells like levitate to remove a melee powerhouse from a multiple opponent fight so your group can concentrate on the rest first.
Special attention should be paid to the old first edition style of wizardy (with only d4 hitpoints it was important) If you cant take the hits, deter people from attacking you. Bluff, or Intimidate your way past the perception that you are a pinata ready to burst. At 4th consider fire shield. (minor damage to those who hit you) Combine that with Blade ward cantrip and possible upcast false life when you are advancing into combat but dont have the opportunity to first strike. Do your opponents want to hit the fighter or the 'easier' to hit mage who makes them burn if they want to attack?
Have fun, your playing a high risk class/subclass. Keep that in mind and let the dice rolls ever be in your favour.