FIRST: GET A PASSWORD MANAGER. period. Then USE IT, for ALL your passwords. Make it your habit. Then use it to make longer, more secure passwords, and change them easily. Truly, it is a worthwhile investment, and loads better than a ratty notebook in the drawer by your keyboard. [End PSA rant]
I recommend DataVault, as I’ve used it for years, and it has never disappointed me. DataVault has stood the test of time, a rarity in the iOS universe. It’s remained relevant and become more powerful and easier to use, without bloating into something it aughtn’t be in the first place. The desktop-iOS integration is seamless, and iCloud sync works flawlessly across my devices. If I remember correctly, DataVault was a month or two behind 1Password to introduce Touch ID (which saves loads of time), but when they update, it works… period. In fact, in all the years I’ve used DV, no update has ever been unstable or flaky–also a rarity for iOS apps. This developer takes both our security and our trust seriously.