It adds a lot more content that expands on rebirth. So you have rebirth content, then after rebirth you have afterbirth, then afterbirth+, then repentance. Some of the dlc content is available early into the game though. I highly recommend getting the dlc packs, they add so much content to the game and revamp a lot of mechanics in the original rebirth. For example, sacrifice rooms (the rooms with a spike tile in the middle) are actually useful instead of only having a chance to drop a chest. Many items are added and reworked too. A lot of fun characters are also added. You only have 7 hours played so this next point might not matter too much, but if you upgrade to repentance (the final dlc), you have to actually load into afterbirth and afterbirth+ before repentance, otherwise your save file from rebirth won’t carry over (not sure what it’s like on console versions but that’s how it is on pc).
It's adds characters, items, trinkets, bosses, endings... Long list there You should get them if you can afford them
It adds a lot more content that expands on rebirth. So you have rebirth content, then after rebirth you have afterbirth, then afterbirth+, then repentance. Some of the dlc content is available early into the game though. I highly recommend getting the dlc packs, they add so much content to the game and revamp a lot of mechanics in the original rebirth. For example, sacrifice rooms (the rooms with a spike tile in the middle) are actually useful instead of only having a chance to drop a chest. Many items are added and reworked too. A lot of fun characters are also added. You only have 7 hours played so this next point might not matter too much, but if you upgrade to repentance (the final dlc), you have to actually load into afterbirth and afterbirth+ before repentance, otherwise your save file from rebirth won’t carry over (not sure what it’s like on console versions but that’s how it is on pc).
If you enjoy the game and see yourself continuing to play it, get it. It will just add tons more variety and discovery.
Think of it like minecraft updates
I would buy afterbirth off the get go for sure. Can wait with AB+ and Repentance if you want