I'm just starting out and I bought the Wilton 53 piece decorating set. It came with 18 tips, 24 disposable decorating bags, 2 couplers, 5 icing colors, a flower nail, a small spatula, and a small book. It was really good to learn with.
Personally, I would suggest buying your tips by the piece. Many of the tips in those sets you will never use!
I always suggest to my students to buy multiples(2 or 3)of the most common tips:
rounds:2,3,4,10,12,
stars: 18,21 or 22, 32
leaf: 67,69,352
rose: 102,104, the really large one-126?
at least 2 sizes of drop flower tips
basketweave: 47 'grass/hair'-199
#7 flower nail
at least 4 couplers, 4-12" bags, and a supply of disposable bags
a tip brush
at least 6 small angled spatulas! 
and at least 2 larger angled spatulas
and a turntable!!
that's all I can think of right now....
I have used about every tip in my kits but that's because I like to make cakes just to practice and play w/ my tips.
I would recommend buying A LOT of couplers and a bench scraper to get your icing smooth is great!
If you aren't going to make a lot of RI flowers.. I'd save your money and just buy tips as you need them. I had a kit a while back, but I never used 1/2 of the tips because I am not into drop flowers and that sort of a thing. I use round tips the most and star tips very rarely. Rose petal tips are useful too. Before you sink a bunch into a load of tips you may never need, sit back and think about what you will want to do with your cakes. Then buy the common tips and add as you need to.
Multiple couplers and icing bags are a must though. 
wow a lot of numbers to learn!!
well when i think about it buying piece by piece sounds reasonable. so, i decided to think about the things i am gonna work and order these ones...
thank you all.
(by the way i am buying many things online from U.S., wilton and such things are very expensive here...)
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