I first read it online as I was overwhelmed with how many volumes there were to collect -- and as a full time University student at the time, it was a lot of money to drop on books that weren't for my classes.
However, I managed to luck out one year and found someone selling Volumes 1-16 for 5 bucks each. I snagged them up SO fast, and thus began my collection. I now only have 4 more volumes to collect and I will be entirely caught up.
My best bit of advice is keep a sharp eye out at expos and comic conventions, and build your collection one volume at a time when you can afford it.
Even make it an effort to order in one volume every paycheck or every month and you'll build your collection at a steady rate!
I can speak from experience that seeing the physical volumes on the shelf definitely beat reading it online.
Best of luck!
