From your list of jobs i would highly recommend looking into laser levels, vastly superior in levelling over an area such as decking, slabs and joists, many people underestimate the impact of cumulative errors in these scenarios, of course you cant beat a spirit level at times but i will say hands down a cross-line laser level is more versatile, first fix; besides leveling to a singular datum of a large area, the laser can be used for alignment, plates on stud walls, headers for door linings, kitchen units, sockets, switches can all be set to a single perfectly level line cast virtually 360 degrees around a room or along a single line down a corridor through doorways etc (picture the crucial first run of boards for a floor) curtain rails and shelves can be levelled visually whilst you have free hand to fix brackets etc in place with ease.
they can as expensive or as cheap as you care to make them, i personally started with a stanley cubix ~£50 currently i use a DeWalt DCE089D1G and at work we use a hilti site laser circa £1600
I know all of the above is totally aside from your original question and i do apologise, in regards to levels those stanley sets are fine, I use stabila I would advocate stabila but stay away from the 70-2 Series types as they are too flimsy IMO
the 96 series are great, 196 are i think the same with handles and the type R are also great but probably not necessary for yourself.
in terms of lengths most of the industry get by on a boat level, 600, 1200 and 1800 if budget is tight id buy one at a time and get the best you can in the size you need for that part of the project, you can always attach a smaller level to a straight edge to cover a span if you're in a pinch and regardless of what you buy, use string lines they are overlooked by too many.
i hope some of my ramblings are of use to you and please feel free to message me if you are close by even if its just to show you how fantastic a laser level is!