i dont want my iphone and ipad to have the same stuff on it i want them to be seperated

You can turn off iCloud syncing for specific things via Settings > [username] > iCloud > ... (e.g., contacts, calendars, reminders, notes, photos, etc).

You can delete apps from one without deleting from the other and you can turn off Settings > iTunes & App Store > ... items in the Automatic Downloads section to stop new purchases downloading to the other device.

You can turn off specific Continuity features to separate the devices: Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch - Apple Support

The above may or may not help depending on what you are including in "same stuff." If not, you may want to reply with more details.

I didn't either. It made my storage go crazy. You need need turn off icloud sharing in settings. And be really careful first. Because depending on where the (let's say picture, could be contacts) picture was added from, or taken on, you can loose it if it's not in the right place when the mess is tidy. I'd fiddle with the message and FaceTime settings also if other ppl have access. Same with app store settings. There's one that says "automatically download apps across all devices and updAtES" that's not horrible but I don't need them all on both. Lots of settings to change. Make sure you check out the location privacy too. Took me hours to make it good. There's so many add ones and reports being sent via cellular and blah blah, some are really deep in. Like more than two pages in one settings options. The very bottom of the privavy page. They snuck some new ones in I would turn off asap. Always remember to back up your data to iTunes as well

That part I understood. I was thinking you may want to be more specific about what things you didn't want on both devices.

My reply covered many things that you can separate while using the same Apple ID. Another option would be to use two different Apple IDs but that is rarely a good idea.

Never create more then one Apple iD it's a horrible choice. It should never be in option unless you are making one for a friend