Breast pump advice??

Amber • 20 years old, mumma to my beautiful boy Oliver and expecting my second in Jan 2018 👶🏼
First time mum and I'm planning on expressing a lot of breast milk and storing it in the fridge/freezer but I'm not sure which product to buy. Manual pumps are obviously cheaper but are the electric pumps worth paying extra for? I'm not sure what brand either, I was thinking of getting Avent and buying all bottles and accessories with that brand but I'm just not 100% sure!