Can you be a winning player without GT?

I am sure it is doable, but no matter how good he is, learning to use GT and PT well will ad very significantly to his winrate.

I personally would rather start with a 200BB bankroll and a new computer than with 300BB bankroll without having the benefits of GT. If he has the bankroll to play 5/10, he should by a new computer!

On the other hand - I would much rather meet him on the 5/10 tables without it :-)