Even though you technically don't roll for (or buy) abilities until after you've chosen your class, it's certainly worth bearing in mind what each of your stats do as you put your character together. The Stat Priority for a generic Wizard is:
Int > Con > Dex > Wis > Cha > Str
Useful for very little indeed without you going out of your way to give it value. The only time this ability becomes relevant is if you want to go 100% down the traditional route and give your Wizard a quarterstaff. If you do, and you for some reason want them to use it in combat (you crazy cat!) then Strength will be what determines their Attack Bonus and Damage modifier.
Good for protection because your Dexterity modifier will be vital for raising your AC and making you harder to hit. Wizards are not proficient with armour, so this is a really key consideration if you don't want to be hit by every arrow, bolt, stick and stone thrown in your direction. The higher your Dex bonus, the more likely you are to survive, and ideally you'll want to pair this with a decent Constitution so you don't croak it the first time you take damage.
Dexterity is a common saving throw against spells that do damage in a large area, too. The icing on the cake is that it will be the relevant Ability for a dagger if you choose to start the game with one, both for throwing it (please don't, you have spells!) and for fighting with it in melee combat (again, please don't, you have spells!)
Good for raising your Hit Points, particularly at level 1. Wizards have the lowest hit die in the game (d6), which means you start with a measly 6HP unless you've boosted your Con to add a couple more points. It's always worth doing this, just for survivability alone, but there is one more bonus to be derived from this ability.
This Ability also has some relevance for your spellcasting, believe it or not. If you cast an ongoing spell with the concentration attribute, having a high Constitution will help you not to lose focus if someone comes and kicks you in the pants mid-cast. Or if they, you know, stab you.
This is your primary, Primary, PRIMARY ability score. Embrace it with all the magical love in your heart. The more of a bookworm megaboffin you are, the more powerful you are. Knowledge really is power in D&D, and it's the kind of power that allows you to deliver a white-hot blast of fiery death directly to someone's face. This governs your Spell Attack Bonus, you Spell Save DC, and powers up some Wizard-relevant skills.
On top of all this, four of the skills on offer from your Wizard bundle use Intelligence – Arcana, Investigation, History and Religion. If you choose any of these skills, they are likely to be naturally good as you pump points into your primary stat.
Wisdom will help you to make saves on 'control' spells, like Hold Person, or Suggestion. If you fall victim to a spell like this that lets an enemy control you then you're likely to turn some very powerful magic against your friends in short order. Naturally, they'll be very angry about it (if they are still alive enough to be angry!) You also have the chance to take a couple of skills that rely on Wisdom (Insight and Medicine), so this is a stat that you can show a little love to if you feel like it, even if it's not the most important.
In terms of the bare bones, this is not vital, although it's beneficial to have a decent Charisma for certain builds of Wizard (the kind that live inside people's minds, rearranging the furniture as they see fit, and have them singing like caged birds with a click of their fingers). If you don't rely on that kind of play style and charming people isn't your cup of tea, you can completely abandon this Ability and be anything but the life and soul of the party. Until someone needs fireballs, and then it's your time to shine!