Hey MomaFugger,
By 'add items together' you mean stacking?
I personally never use arrays for inventories. You can just do it this way (not completely checked for bugs):
c3p: https://1drv.ms/u/s!Ap_-qxoGKbDceT8PkGeTDqQ8jaw
After the items are in the inventory, you can still count them out and transfer them to an array or dictionary if needed.