Can i use a iphone without a sim card?

I want to buy an iphone from ebay can I use the interenet and play games, can I do tht without a sim card

I doubt it. It's a phone. Just buy an iPad.

Yes you can, you can activate it with any inactive sim card. You will then connect to Wi-Fi only.

No, you can't get past the startup screen without inserting a sim card first.