If funds are limited then buy individual tools as you need them – if you buy a ready made tool kit you will waste money on tools that aren't required for your bike.
If every time that you need to do a job you buy the tools required for that job it'll spread the cost of building up a tool kit, and allow you to build up a set of good quality tools over time.
If you don't have any tools at all then start with a multitool – you can keep it in your bag when riding, and use it when doing simple jobs. It is however, not a good replacement for the proper workshop tools in the long term.
With tools there seems to be a simple rule – buy cheap, and have a frustrating experience doing a job, screw up a component when the tools slips and then have to re-buy the tool when it breaks prematurely OR buy good and buy once, and enjoy maintaining your bike.