A physical journal, using the bullet journal method is what works for me. It is hard to stick to it the first few months and require a good amount of effort but that's what I've been the most persistent with.

The book "The bullet journal method" from Ryder Carroll was a good introduction to understand how the method works (try to ignore the preachy tone): https://bulletjournal.com/pages/book.

I now have >6 months of journaling, with only a few missing weeks and I can say it has been very helpful to organize my time and mind.

Regarding the type of notebook or pen, it really does not matter, you just need something you enjoy using. I personally use Faber-Castell pens I got for a few cents each (in €) because I like their feeling in my hand, and an idena notebook because they have a lot of pages and I already had a few of them around my house (~6€ each).