Boots for under $100 would be hard to find. I don't believe in skimping on boots. You should probably consider something closer to $150-200 for good boots. Even with great deals, it can be hard to find them cheaper.
This is coming from the guy who just spent $1.04 on his wife's new Burton Emeralds, though. If you look, you might be able to get something super cheap. Ridiculously cheap, even.
I ride pretty much your style and I have Rome Arsenal bindings and Vans Cirro boots. The bindings were around $100 when I got them, but the boots were $260.
One thing I would recommend is getting some strap ins. I thought step ins were convenient, but they don't offer the performance of strap ins for all mountain riding, in my opinion.
Rome Design 165 / Rome Arsenals
Rome Anthem 158