my 2 cents :
1) buy a router, it doesnt make a difference what brand or model provided you buy it locally. do not buy it online. any faults or defects with it will cost you time should anything have to be sent back for a refund or repair. and when i say any router, i mean any router. all you will be doing is light work, so price range from 30 euro to 60 euro will do.
2) buy a jigsaw. and i mean a proper one. get one with a good thick metal base. all jigsaws that are cheap are only good for a months work. the reason why is because the front of the base bends over time with use. so if you buy cheap, it wont last long. buy a good heavy duty jiggy, and you'll be set up for years. i have a good hitachi and the base on it is 6mm thick. all cheap jiggys have a 1.5 to 2mm thick base, and they are worthless. its not about the motor contained within a jigsaw, its about how well the machine blade cuts through materials while it maintains a 90 degree angle to the base of the jiggy.
3) buy yourself a good quality roofing square. its a one piece aluminium tool that is triangle shaped. do not buy a carpenters square, which looks like a large " L " shape. they can be off by as much as 1 degree from the factory, so only buy the roofing square as its a one piece design, and the angles are 100% accurate.
finally, never use a jigsaw on a edge that you evetually intend to butt join to another piece of timber.
jigsaws are not, and i mean NOT intended to cut straight lines. they are for cutting shapes and circles. only a router or circular saw should be used to cut a straight line.
as a tip, pre-cut all shapes / circles on spare mdf and then use them as templates on the good sheet material.
look at my arcade cab videos in this section. you'll see what i mean. its titled " woodworking 101 ".