Is it too late for me to upgrade?

Overview:

I bought my MacBook (13.3 inch, Black) late June of 2007, making it a little over 5 years old.

My OS X is currently 10.4.11 and hasn't been upgraded in, obviously, years.

Of course it annoyed me that I couldn't download certain things or upgrade my applications but, I put up with it because I thought it would be too much of a hassle to go to the Apple store and buy it - plus did I really need to spend how ever many dollars to change something that worked fine enough? So, the years went by....

Recently, I have needed to buy programs and software that require 10.5 or newer (for example, I just recieved a new iTouch as a gift) and I am sort of panicking.

Now, I was under the impression I wouldn't be able to upgrade to 10.5 because the newer Macbooks have a new Intel chip... or something like that, I can't remember what I read exactly, so it wasn't compatiable anyway. Maybe I read it wrong or the person was mistaken or I misunderstood (that tends to happen a lot with me) or etc.

I know that I cannot buy the 10.5 disk at the Apple store anymore and that I will need to buy it on ebay or amazon or some other seller.

But, I am still worried that I will not be able to upgrade my OS, and there is no room in my budget to buy a new computer.

Can someone help quell my worried mind? Haha.

One more thing - if I AM able to upgrade to a higher OS X, can I just skip to the most recent one? Or is there some way I can buy a bundle of the past OS Xs and by pass all this nonsense of having things not work for me because I am not fully up-to-date and possibly save some money?

Thank you in advanced!