With regard to budget to fly a spi.

I'm still sailing with my 2003 kite, they can last quite long. The AHPC snuffer system costed me 250 US$ and works like one of the best. Spi itself should costs about 800 US$. Other hardwire and lines should cost no more 400 US$ in total. In short the costs have come down considerably in the last few years.

You can do it even more cheaply if you find yourself some secondhand I-17 or F16 spi. Sure enough these are around especially since the heavy boys in the I-17 class may now use a larger spinnaker ?

Personally, after knowing what I know now about sailing with a spinnaker. I would give it a good try getting one for he budget that you may have.

Wouter