How to improve my singing!?

Well, I am starting to improve my singing for the vocals for my band. I have the characteristics to become a singer; plus I was amazing at singing when I was young. Then my singing went from amazing to alright, I didn't sing for more than 10 years until I formed my band. Is it b ecause I quit singing over 10 years, and my vocal chords didn't develop as time went by. Another problem, when I sing my voice is nasally, I blamed my allergies because it is hard to breathe through my nose,and I have to breath through my mouth. Only problem I had was a nasally voice when I sing. Before I waste money on a private singing lesson, is there any ways to improve it, like drink cold milk before I practice, etc?