First notebook entry: Introducing myself

I want to learning English. I need a practice.

"Wanna" is poor English. Don't bother using it; it makes the writer/speaker seem simple-minded and lazy.

You are right to keep the sentences separate. They can't be joined with a comma.

"Practice" or "to practise"(ie. the action) are both possible.

First notebook entry: Introducing myself

I wanna learn English, I need practice. 

First notebook entry: Introducing myself

I wanna learning English. I need a practic.

I want to learn English, I need practice
I wanna learn English, I need practice 

First notebook entry: Introducing myself

I wanna/want to learning English. I need a to practice.

I hope this little corrections could help you a lot in learning English language. Thank you.