You can do "The Bullet Journal Method" digitally. See how I do it and the apps I recommend: https://www.theawesomeplanner.com/the-bullet-journal-method-digital-version-onebookjuly2019/
My #1 Device
I love my iPad Mini 6... Pink, Wi-Fi + Cellular, 256. I purchased mine through T-Mobile but you can get a renewed/practically new one on Amazon HERE. This thing can go with you everywhere and can even fit the in the back pocket of many jeans!
You can find a list of my devices and favorite apps on the 'Resources' page.