Hello! =D
It actually depends on what kind of theme you like actually. But I guess you don't necessarily need to buy the props if you want to cut on some costs here though, items from home can work equally well. You can also consider adding a personal touch to your shoots using some items that are representative of you and your HTB, like for example, if you guys are into music, a guitar or any other portable instrument would come in handy! Probably something like that!
Bubbles are really useful as well, gives the dreamy effect. Or small pets can make your pre-wedding shoot a whole lot more cute and fun! Alternatively, you can make the shoot into a story or a process that involves something that you both enjoy doing. Wine glasses, baking equipment, pillows, umbrellas, luggages, soft toys, flowers, handmade signboards, anything works if you can make it your own! Have fun!