Everyone is different. I personally bought a tablet from amazon (Samsung Tab A7 lite) and use the Tomtom go navigation app (it has a HGV setting). I've been using it for years, has live traffic, can select different routes, allows you to enter vehicle height, ADR, finds fuel stations for etc etc.
You have to pay for it. It costs £8,99 a month, (or £2.25 a week) which is nothing,
Plus when you are on a loading bay /break POA you can use it to watch Netflix, check emails and so on.
Tablet I use Samsung Galaxy Tab A7 Lite 8.7 Inch Wi-Fi Android Tablet 32 GB Grey https://amzn.eu/c7tsRlR
And the tomtom app https://play.google.com/store/apps/details?id=com.tomtom.gplay.navapp
You'll be fine from that. An app I used when I started 8 years ago is called Trucker Timer: https://play.google.com/store/apps/details?id=com.spottydog.tt
Works pretty well for keeping track, I wouldn't bother with the GPS feature though.
Also, don't listen to other comments saying to not put your card in immediately. You absolutely should and manual entry it to when you started work (I.e got to be traffic office to get the keys).
OK there is many hgv theory learning aids online and apps. Some free. Some you pay for.
I personally used a site called drivingtheory4all.com
They had not only the theory study aids on there but also the cpc help as well. It cost around £18 for 3 months. The thing to remember about this site is, it's not the tests you do on there that matters. It's the study material.
But there's also hgv theroy apps as well https://play.google.com/store/apps/details?id=com.deepriverdev.lgv.hpt For example
I used this app.. Useful to have something in my pocket to look at when I had a spare five minutes, or just before to went to sleep. I did get the DVSA theory book as well, but didn't use it much. The app can give you the HPT practise videos too.
There was a very long waiting list at my local theory test centre, so had to wait for a space. Probably could have kept calling for a cancellation.
I'm not a big fan of Satnavs personally, but I can see that they have their place.
I found this app, called "Road Lords" recently, and have been testing it. It's not sent me wrong yet, and the ETAs are pretty accurate, unless there's traffic. It's a bit shit at traffic even though it knows about it, so I tend to have a look at Google maps for traffic.
But it's free so worth giving a try