To be honest at that young age YOU are still the best toy for your LO. As long as you spend time singing, doing nursery rhymes & songs with actions, pulling faces, blowing raspberrys, playing peekaboo behind a muslin cloth etc. etc. you will keep your LO amused.
Oliver just had a few soft toys at that age. A few musical things too. Rattles.
I made some toys too - empty water bottle filled with buttons/rice/dried pasta - to create rattles. He loves chewing a shower scrunchie (!). wooden spoon. ribbon dangled over his face.
I think you should only leave him in the bouncy chait for 30mins at a time.
Its when they get a bit more aware &/or mobile and start to be able to co-ordinate and grab things that you need to invest in a more toys.
I agree with Lisa - car boots, charity shops & EBay for 2nd hand toys keeps costs down - as long as you can wipe them over with a steriliser (I personally wouldn't get soft 2nd hand toys).
I'm just starting to think about Christmas & am already bidding on things on EBay