Having lived in China for a few years now, I have learned a lot about screws. There is a tendency to get hung up about using the right screw, I used to be guilty of that. Unless you are doing cabinet making, there is no need.
In my workshop I have a reasonable range of screws, but only seem to use a few types.
I was passed on some good learning by Dan, an apprenticed chippy. There is one screw that will do everything, the drywall screw. If it is not going to show (you can always countersink and cover), it does not matter. Super hard and super sharp, there is no need to drill pilot holes, and they are even sharp enough to drive directly into steel boxes without drilling first (I have driven into 2mm box girders before).
There are regular brassed woodscrews that I buy, by the kilo (20-30rmb), these are soft, but you
must drill pilot holes. I get these at a trade supplier.
I also use pocket screws, 90% of the time 1 1/4", for pocket jointing in 3/4" (15-18mm) ply.
The only other specialty screws I use are hinge screws, but they come with the hinges. B&Q are good for hinges, the budget brassed
hinges (50 and 75mm) are 5rmb for 2 pr.
I use 5mm wall plugs, and as the screws will usually be hidden, I use any suitable length/dia screw I have.
I also do a lot of nail and glue joining. The nails just hold things fast while the glue dries. PVA is cheap and the joints are stronger than the wood if properly used.
My must have tools are:
Small claw hammer.
Cordless screw driver (cheap ones are smaller and get into tighter spaces.
Good quality driver bits (Bosch come in sets of 10 at B&Q)
Combination square.
Pencil
Tape measure 5m
Pliers (regular and long nose)
Add a deadblow hammer (orange plastic thing) cheap, as I do cabinet making.
These are the tools I use almost daily.
If you want to meet up in the south, I will show you where I buy my hardware in DaShangHui, near Qianxing Lu and Guangfu Lu.
Where you can buy good, reasonably priced power tools, and where I buy my quality plywoods. PM me if interested.