Q: How do I delete my pictures in Icloud so that I may put more in without buying more storage?

Photo stream photos don't count against your storage so deleting those won't help.  Camera roll photos are included in your iCloud backup, which does use your storage.  To turn these off, go to Setting>iCloud>Storage & Backup>Manage Storage, tap your device under Backups, then turn Camera Roll to Off under Backup Options.

If you do this you will no longer be backing up your photos to iCloud.  Be sure to import them to your computer for safekeeping so you don't lose them, as explained here: http://support.apple.com/kb/HT4083.

This article may also be of interest: http://support.apple.com/kb/ht4847.

If you are maintaining a large number of photos in Camera Roll get them sync to a computer, in it's backup and resync them to your device through iTunes.This way they are backed up with your computer's backup, on your device and not taking up iCloud backup space. This way you can now delete all the photos in Camera Roll and still have them on your device. Now with a cleaner Camera Roll ther would be no need to take it out of the iCloud backup. This way your new photos can be in a backup till you get time to transfer them into you photo library on the computer.