Heyas! Welcome to the community.
On the most basic level, playing a spellcaster is more about using what you have than fancy builds. You can do all kinds of awesome and crazy build stuff, but learning the fundamentals is important. The best spell slinger is only as good as the magic he has ready.
Here's something I typed up earlier that might help, keep this in mind and even an out of the box wizard with a good INT score can kick all kinds of butt:
Spell Casters can do a lot to help their party.
Direct Damage is the least efficient. That doesn't mean you NEVER want to take a damage spell, but you really need to weigh damage which is something anyone can do with the stuff only spell casters can do. A wizard focused on damage is like playing a glass cannon in a party full of more durable guns of smaller caliber.
Buffs and Debuffs: In my opinion, buffs are fine but debuffs are too hit and miss. Debuffs usually have saves attached where the target gets away mostly untouched. Any really good debuff usually falls more into the next category "Battlefield Control" because it is so reliable and devastating. Buffs make the party better at what they're already good at or shore up a weakness. Example: Monks can't wear armor but need to get into the thick of combat. Throw Armor on the monk, and he's a LOT harder to hit, at least at low levels. Or hit him with Enlarge Person! Reach + Size Bonuses makes a very effective melee combatant. If you know you're going up against one really tough opponent, you might find some good debuffs to sling around. It isn't usually worth it to make one of twelve identical monsters blind or slow or weak. But slowing The Boss might be worth it if he has few henchman or they're really weak compared to the party.
Battlefield Control limits the number of enemies your party has to deal with at any given time. Six heroes can't fight the entire Orcish Legion in one go. Using spells you can trap groups of enemies in webs or behind walls. You can hit groups of enemies with save or suck or save or die spells and then fight whoever makes their save. If you drop Sleep on a group of eight enemies, and four of them fall asleep, you've cut the number of guys you need to fight IN HALF. It doesn't last forever, but you can take advantage of the temporary number advantage. One spell just turned the entire battle around for your party and it didn't do any damage! Glitterdust is a great spell in that regard. It reveals invisible stuff in the area, and it blinds anyone it affects. Cast is on a group of guys, if half are blinded kill the other half then deal with the guys who can't see!
