Thanks for the

Tom!
I had actually typed up a detailed reply to GMT on my phone earlier and then hit the wrong button and deleted it, decided to wait until I could get on my laptop to redo it.
GMT - I can't remember where on the island you are, sorry. My replies are appropriate for the Northern half of the island, Archer or someone else will probably have better info for further South.
Firstly - there are very few wild goats these days since the Cabildo did a round up a couple of years ago. Unless you are literally in the middle of nowhere and have no boundary fence/wall, you are unlikely to be bothered by them.
Rabbits - again, mainly in uninhabited areas, so if you border the natural park or the dunes for example you may encounter them. I saw plenty on the dunes beach at Corralejo but most properties that border that area have walls/fences/dogs, so didn't have any problems with them. It is a different matter in Tindaya, there is quite a large population living in the scrubland and providing food for the guirres! Luckily my garden is completely enclosed and the only rabbits that have got in have been babies that could get between the bars in the gate. A local friend has a humane rabbit trap that we share as needed as they rarely find their way out by themselves! We let them loose down the lane (and the occasional cat that has been tempted by raw carrot!)
Ground

s - vermin! I've never knowingly had plant problems from them but there was quite a large population living in our garden walls when we moved here. Rat bait Tbag things in a bait box solved that. Make sure you hunt out dead ones and put in the wheelie bin so birds don't eat them.
Cats are the biggest animal pest for gardens in urban and rural areas. The law states that all animals must be kept in the confines of your property and only taken out on a leash, but most cat owners don't seem to think this applies to them. In my experience cats have scratched the bark on trees so much that infection gets in and the tree dies. Or they scratch up or lay on top of seedlings and young plants. Or, joy of joy, they use your carefully tended flower and veg beds as toilets. I have a friend who has cats - she says to me, "Cats don't make a mess in the garden". No, not in hers they don't but she lets them out every night and they go in other people's gardens where there is soft, tended soil or picon. Sorry, pet hate, rant over.
Insects. You are more likely to encounter damage from insect pests than anything else. Greenfly, blackfly and every colour in between. Stink bugs. Soldier bugs. Moth caterpillars. And biggies here, cochineal and scale which are farmed by ants. Keep the ants at bay and you will minimise attacks by cochineal and scale.
Steel - El Norte in Corralejo have everything metal and make stuff to order.
I tend to use rebar (heirro) which I get cut to the required lengths from the ferreterias Brikogar or Fenimoy in Villaverde. One advantage of this is that as it starts rusting it puts ferrous stuff into the soil, something sadly lacking here and very necessary for most plants/trees. I keep a pot in the garden that I put all old nails etc in and then tip the contents into the bottom of the hole when I'm planting. Builders offcuts of rebar are good for this as well. Failing that when you buy fertiliser get the blue granules that have heirro granules in as well, saves buying separate ferrous products and doing separate feeds.
Brikogar also sell varieties of metal fencing by the metre - I bought some recently to make some surrounds for new plantings, but I put windbreak netting over it and use it as a shade and wind protection until the plant gets established, rather than pest protection. The plastic fencing comes in rolls and can be bought at most ferreterias, I just prefer the metal as it lasts so much longer. Plastic outdoor products here have a pretty limited lifespan due to our UV levels.
One of the most important steps to successful planting here is to incorporate a soil improver in your ground. You can get it from
Happy Plants and it is Coco fibre based. Using peat (as in most cheaper bags of compost sold all over) is a mistake here. It holds too much water leading to rotting stems/drowned roots, and it decomposes pretty quickly and washes away leaving your trees with air pockets around the roots. Fenimoy in Villaverde stock
Happy Plants Soil Improver substrate (Terra Nova) if that is closer to you. I rarely get it from there, any excuse to go to
Happy Plants!
When planting what will be trees/large shrubs it's useful to incorporate a large pipe into the hole so that when you water you can get some right down into the roots rather than just on the surface.
Good luck, remember to do before and after pics as you get your garden going! Ask as many Qs as you like and let us know what works well for you. As with everything, what works well for 1 person/place doesn't necessarily work for others.