If you are the type who blows thru content really fast, going VIP until you get your character past level 50 is a good idea.
If you have very limited playtime, like to take it slow, or just want to buy the content as you need it, then buy a package of Turbine Points and become Premium. Buy quest packs as you want them
If you don't want to be bothered with deciding what content to buy, go VIP. You have all the non-expansion stuff plus 500 points per month for whatever else you want to buy.
If money is tight you can choose to grind for your TPs instead of buying them. Stay a Free player.
If you are frugal, go VIP for a short time (1 - 3 months), and create all the characters you are interested in during that time. You'll get 500 points per month, and all your characters will have some stuff unlocked that Premium players ordinarily would need to spend points to unlock.
VIP isn't for everyone. If you don't see the point in it, don't go VIP.