It's fine. That's the construction which any native speaker would use in most situations. If you want to follow the grammar book to the letter, a pedantic teacher might insist on this: 'I want to find a person with whom I can practise my language skills.' The combination of neutral, everyday words with the formal construction 'with whom' sounds unnatural, however. It's not something which a native speaker would be likely to say. Probably the most natural sentence is this slightly neater version: 'I want to find someone to practise my language skills with.'