Wait for the 4U would be best the TF isn't as good as a 4U is from any of the other series I'd suggest a 15th idl as that's the best of the choices in my opinion.
If you plan on getting a non-color tama I would recommend the 4.5, because it has a lot of features. If you want a color tama the Tamagotchi P's or 15th Anniversary iD L would be ideal.
i heard 4.5 is good even though i don't have one. imo, i think 3 is good. for colors, wait until 4U or get an iD which some guy on ebay called charliefby sells for really cheap! got mine from him for 40 dollars! but they have some dirt and scratches. small ones, though, so don't worry!