Newb question for class on my first playthrough

Ive played dnd 3.5 and 5e a bunch but I dont really understand this system very well so I wanted to run my idea by you guys before I find out i hate it and need to restart. I like the idea of playing a mage and immediately dual classing into fighter. Basically my idea is that I want to be a basic fighter with the versatility of wands. However I dont know if this is dumb or what the trade offs are beyond the downtime. I get i can not use my own spells with armor on too, thats not a big deal.

Any obvious pitfalls I am falling into with this? Any advice on stat,spells or kit choice?