Actually spending that much on one would be the hardest part. But I would love to build one. The biggest one! Hah
lol yeah it goes something like this:
1/144
1/144 HG
1/144 RG
1/100
1/100 MG
1/60
1/60 PG
1/144 in my opinion is too small, though 1/144 HG has decent amount of details and 1/144 RG just hurt your eyes. It's tiny and has A LOT of details.
1/100 is what I'd normally recommend it's cheap, decent quality and big enough. Though typically I only buy 1/100 MG myself.
1/60 is pretty big but it's usually very lacking in details, so it look a bit plain at times. 1/60 PG is basically big and has lots of details but expensive.
And depends on how hardcore you get some people would airbrush them but I'm too cheap so I just get a fine thin marker and marker in the detail lines. You can use eraser if you draw it wrong somehow it will erase markers on plastic.
http://dalong.net/ is a pretty good Gundam site this guy buys everything there is. Granted we can't read Koreans but it's nice to see the pictures, you can navigate through the top.
http://dalong.net/review/mg/m72/m72_p.htm This was the one tp4tissue used to make that keycap