My suggestion is to not skimp on good boots. Go get properly measured in-store and allow yourself some time to wear the boots in before going on your first major trek. Your feet are going to be responsible for getting you to and from your locations safely. Boots that seem fine after a few minutes wear can be agony after a few hours.
If you're going to be climbing then you're also going to be descending too. You should take this into account when breaking in new boots because these activities will place different stresses on them.
When choosing the type of boot to go for, have some expectation of the type of terrain you will want to cover and the type of weather conditions you'll be walking in. A soft-soled boot designed for valley walking in the summer isn't going to provide the same support as a boot designed for scrambling rocky surfaces.
Get a spare set of laces and carry them with you. They're your boots' lynchpin. If they fail then your boots will not be able to function properly.
Learn about the different ways in which you can lace your boots up. They can make a huge difference in the type of support your boots provide.
Invest in good quality walking socks and consider liners too. Wearing ordinary cotton sports socks means when they get wet they will rub against your skin and cause blisters. Socks designed for walking will allow your feet to breathe and layering socks means that the socks slide against each other rather than your foot against the sock. The result is less foot fatigue and less chance of blistering.
Take blister plasters on your treks, for obvious reasons.
For any decent amount of walking, I'd usually recommend walking poles. As well as sharing some of the effort from walking with your upper body they can be useful for providing support especially if you've dodgy ankles and are susceptible to twists and falls. The difference they make is worth the extra £20-30 for a cheap pair.
Some articles and reviews for you to read -
http://www.livefortheoutdoors.com/Gear-Reviews/left-hand-nav/Footwear/