Nobody Really

Not at all. Just as "Duel Monsters" ("Yugioh's TCG's in-universe name) was originally a MTG reference, Pegasus was meant to in some way reference MTG's creator in some unorthodox way. Kazuki Takahashi is more of a gambler than Pegasus ever was. In fact, Pegasus is the opposite of a gambler when you factor in his original dependency on the Millennium Eye's power to see through the answers of said "gambles".

So Kazuki Takahashi's YGO counterpart would Joey.

If I had to guess off the top of my head what character resembles him most, it'd probably be Solomon. Kazuki actually liked making a bunch of custom games that only appeared once in the manga and then moving on to creating a different game with instructions and pieces at the end of a few of his manga. His card game wasn't really the only focus and he is more of a gambler than anything. Which Yugi's grandpa actually had a lot of risky plays in his youth. I think it'd be what fits better.