Welcome to Final Fantasy XIII Forums! A forum about Final Fantasy XIII and all other games in the Fabula Nova Crystallis compilation! Our forum has grown to become one of the biggest communities dedicated to Square-Enix's future titles and is growing even larger thanks to everyone already participating.
We can see that you are a guest on our site and would recommend you sign up to our forum by Registering and joining in. Registered Members can participate by posting in threads, using our Chatbox, buying forum items from our Store and enjoy it all advertisement free.
The best decision at this point is to get the Weapons for your party of choice to Tier 2 max right now. You can go back and do Missions 1-14 until you get a Chocobo. Afterwards, you can find treasures that can transform Tier 1 -> Tier 2 instead of paying (you'll need to unlock the Ultracompact Reactors which cost 50k in the R&D Depot Store).
Still, it will take a long time which your only choice really is to go back and grind and proceed onwards with the game. There are certain parts you need to unlock before you can take advantage of Weapon Upgrading (like the Adamantoise in Chapter 12).
I'm only on Chapter 4 but I'm enjoying it a lot. I think people are disappointed that it doesn't play more like a traditional Final Fantasy. They've attempted to make the combat much more fast paced and that means they've had to change the battle system pretty drastically. Some people are annoyed by that and even I usually dislike change but so far it's extremely fun and very intuitive.