if i share the same apple ID with someone, but have a different icloud, will my messages, photos, etc go to their device?

An AppleID is an iCloudID. You'll still have the same problem.

Create and start using an Apple ID - https://support.apple.com/HT203993

Set up an Apple ID to use in the iTunes Store, App Store, or iBooks Store, and with Apple Music and Apple News - https://support.apple.com/HT204316

Frequently asked questions about Apple ID - http://support.apple.com/kb/HE37

You can leave the shared Apple ID signed in to Settings->iTunes & App Stores, and use your own to sign in to iCloud, and Messages, and Facetime.

Note that if ever you want to split the purchases made on the single Apple ID, it will not be possible, and the owner of that ID will keep those purchases.

In the long run it will be more trouble than its worth to keep a single Apple ID for purchases.