I recently purchased a curado g6 and a citica. the salesman at the store told me to always have at least two brakes on opposite sides of each other at all times. I have just been using one brake as i am used to casting reels. any input?

You'll be fine if that is working for you.  It is usually recommended that it would be on the opposite sides if you have 2 on..etc. There isn't a requirement or anything.

I read up generally if you need two to use opposite sides but two was slowing my casts

That's for people that need more than one. Cast away.

One brake is fine to use if it gives the results you want. When using more than one it's best to offset them equally around the spool.