All you have to do is add to the shopping list.

For example
I went to the shop and I bought an apple.
Person Reply's with: I went to the shop and I bought an apple and a banana.
Next person reply's with: I went to the shop and I bought an apple, a banana and a can of soup.
All you have to do is that ^^^^.

Let me start you off:
I went to the shop and I bought a Video Game.

I went to the Shop and buyed a laptop

Buyed isn't a word. And you have to include what he said. (And isn't this a game somewhere else =P I dunno)

I went to the shop and bought a video game, a laptop and a packet of crisps.

I went to the shop and bought a video game, a laptop, a packet of crisps and Sushi.

I went to the shop and bought a video game, a laptop and a packet of crisps, sushi, and a roller coaster.

I went to the shop and bought a video game, a laptop and a packet of crisps, sushi, a roller coaster, and an elephant.

I went to the shop and bought a video game, a laptop, a packet of crisps, sushi, a roller coaster, an elephant and a karaoke machine.

I went to the shop and bought a video game, a laptop and a packet of crisps, sushi, a roller coaster, an elephant, and a train.

Oh dear, looks like you'v broken the chain, let me correct you:

alexwohlbruck says: I went to the shop and bought a video game, a laptop, a packet of crisps, sushi, a roller coaster, an elephant, a karaoke machine and a train.

I went to the shop and bought a video game, a laptop, a packet of crisps, sushi, a roller coaster, an elephant, a karaoke machine a train, and some pony merchandise.