Depending on your requirements you might already have a device that might meet your needs for very little outlay.
Most smartphones have GPS in them nowadays and with some free software you can start to get comfortable with GPS navigation.
There are pro's and con's with this route and it might not be right for you.
For example
I use a Samsung Galaxy S7 with "Viewranger" software
www.viewranger.co.uk
This cost me £0 initially as the software is free and I already had the phone, for free you only get openstreetmap and satellite imagery (but I quite often find that openstreetmap is better than ordnance survey maps)
Viewranger does all the classic GPS stuff (Recording trails, Route following) plus some features you won't get on a Classic GPS device (Reporting your location to your family/friends in real time, Virtual Reality skyline)
Pro's
Can be much much cheaper.
Assisted GPS (Helps get a position lock much quicker - usually in under 2 seconds)
The best web based Route editor, I seen.
Multiple map sources (Openstreetmap, Ordnance Survey and Satellite imagery) - for £25 a year you can get 1:50000 and 1:25000 Ordnance Survey maps, which are also available on the Web route editor (Satmap want you to spend Hundred of pounds on SD card based ordnance survey maps and then another £25 to use them on the their web based editor)
Has Openstreetmap Map data - I've found Ordnance Survey data to be wrong in a number of occasions or not enough details, while Openstreetmap can also be wrong it can be a second source of data. I can also easily fix anything that is wrong with the openstreetmap data by contributing maps updates. Openstreetmaps also has a lot more Permissive paths than Ordnance Survey.
With the Samsung S7 it has a better waterproof (IP) rating than some classic GPS devices.
The software is more responsive than some of the classic GPS devices I've tried.
It is integrate with an active community of route publishers.
Con's
Battery Life - not as bad as you think. For me with the S7 for 7 hours of just trail recording will leave me with 65% battery left, 7 hours of trail recording and route navigation leaves me with 35% battery, but I have cheap addon battery pack that will quadruple that life. (using the screen is what drains the battery)
It will use Data from your phone plan - but with pre-planning by download/caching wifi I generally use only about 100Mb a month, so even a very cheap plan it won't cost much.
It is combing your emergency communication device with your GPS device - as you are then using it more it might be more likely to be dropped/broken/run out of charge.
I don't have any relationship with Samsung or Viewranger and my experiences are based single day based UK rural (but not totally remote area of the UK. e.g. North Scotland) and rural use in France (where I use IGN 1:25000 maps subscription for £18 a year)
(Robert - there is a viewranger version for iPhone as well so you could use that for maps and recording)