should i use this ?

You can get started programming on pretty much any machine. So yeah, while that's kind of an old Mac in general terms, it's easily powerful enough to get started with the likes of Ruby. You only really need to worry about specs if you're getting into some really hefty number crunching or graphical stuff, which most people will never even touch. Programming alone is not an intensive task on your computer! :)

You'll have zero issues with those specs. Writing and running code, bar algorithms, is very light on a system. You got to think, a mobile phone processes exactly the same code as the most powerful computer in the world when loading a website. Writing code itself is as intensive on hardware as writing a word document. The only time you'll struggle is when something is being worked out or converted so image and video rendering and algorithm working. These tasks are where a processor is being asked to do lots of things at once and while any machine will be able to handle it, slower machines will simply take forever to do it and won't respond to inputs. Hence why data encryption revolves around sub-prime numbers but that's a conversation for another day.

thank you