Hi and welcome!!!
I would say you first need to decide whether signature or leather catches your eye, and also what you need for your wardrobe and lifestyle. As Fashionista suggests, take a look at coach.com and see what catches your attention. Better yet, take the time to walk around a Coach boutique, factory store, or dept store. It's always better to view the bags in person because they never look the same as online...especially regarding color and how they slouch without the mountain of packing materials. Some of the bags are also very heavy, which might bother you. At the store, they will let you try to bag on and walk around with your own contents just to see how you like it.
Once you decide on the bag, then you can do price searches and choose your venue for purchase. A lot of the retail stuff is showing up early on at the factory stores, or also you can purchase cheaper on Ebay (as long as you are careful).