Very much a topic that you would get 100 answers to by asking 100 anglers,so I think
the basics are about all you'll need here to get you started and find out what you prefer by experience.
Hook sizes can be very confusing as manufacturers do not have standard sizes which they
all adhere to,and a chosen size from one,will not necessarily be the same from another.
Basically though larger hooks come in sizes which have a suffix of '/0'
By that I mean 1/0,2/0,3/0,4/0,5/0,6/0 etc.
That denotes the size of hook,1/0 being the smaller and obviously sizing up.
Smaller hooks work in the opposite way.There are no prefixes,and sizes 1,2,3,4,5,6,7,8
go down, from 1 being the larger.
In a fishing sense I would choose 1/0 to 3/0 for wrasse fishing for instance,and 3/0
to 6/0 for cod fishing.
I would choose size 1 to 3 or so for small coalies and flounders.
These are all generalisations though and only by fishing for a while will you find out
what suits your own style and method of fishing.
To give you an idea though,a size 1/0 hook is probably about a 1cm gape,while a 6/0
is probably around the size of a 2p piece.
As far as styles go,again,there are many,including Aberdeens, O'Shaughnessy, Limerick,
Baitholder, Cirlce, Semi Circle,and the list goes on.
In basic terms though hooks come as 'J' type hooks which are exactly as the name would
suggest in the shape of the letter. These vary in shank lengths, gape widths, and wire gauges,but are essentially the same
style,and Circle hooks which have a far more turned in point and are designed to catch fish in the corner of their mouths.
Of all things not to skimp on money-wise when setting up your tackle though is hooks.
You can buy very cheap hooks,probably for a couple of pence each but they will be very much inferior to the decent hooks that
manufacturers such as Mustad, Varivas, Sakuma, VMC, Kamasan etc provide. You can expect to pay something like £4 upwards for
packs of 30 or so of most of these hooks,but realistically you are still only looking at something like 20p to 40p each per
hook, and for that sort of money you are getting good quality and it will likely be the main difference in catching fish or
not.