Recently my blackberry has been getting overloaded and deleting my texts and call logs because it has no memory
It's getting really annoying haha, and I'm going to get a memory card tomorrow
I was just wondering how much of a difference do they make? If they come in different capacities what is the best one to get? I take a lot of pictures with my phone and will probably want to add a few applications after I get the card, right now I only have jivetalk.
If anyone could help me out it would be great

The memory card will not make a difference for SMS and email. Follow this link

How do I free up memory on my device? - BlackBerryFAQ

I have a 2 gig card and use it for pic and music and it works fine for me. I would say it depend on how much extra space you want. Maybe 2-4 gig sounds like a good place to start. You can always upgrade