Hello, I already own a Symmar-S 240mm lens and I shoot 8x10. 240mm is about as wide as I want to go. I am looking to get three lenses in total before I go away travelling in about a year. The thing is I can only afford to buy one lens now and another in about three to four months as I am trying to save etc. My question is what lens should I go for first?

I want to get a lens in the 360mm range and another in the 450-480 range so I would have a nicely spaced affordable lens collection 240mm - 360mm? - 480/450mm? What I can't decide is what lens length to go for first, seeing as there will be a considerable time gap before I can purchase the next one? I know it is a fairly open ended question but I was hoping some opinion and advice could be had.

matthew