Lagartun for my money is the best available in North America. Although of their oval in gold, silver, and copper; both sizes of their round in gold and silver (these are used for tips when both a tip and tag is called for because they are so nice and small); both gold and silver embossed; and all sizes of their flat in gold, silver, and copper, to get started, you don't need all the sizes Lagartun offers. Medium flat in gold and silver, extra fine round in gold and silver, and medium and large flat-laying oval in silver and gold are all you need to tie spey and dee flies.
Uni French tinsel is next best in my opinion. Medium flat, fine/medium, and large oval are all you need to get started.
The various mylar tinsels on the market are useful for tying an underbody to put floss over so it doesn't darken when wet. However, because mylar tinsels are not as strong as metallic ones, it is essential for you to put a coat of lacquer (head cement) on them after tying in and wrapping the floss over-body (or on the whole body if a flat tinsel body) to protect it from getting cut or broken by fish teeth or river rocks. Flat mylar in medium is the only size I use and only for underbodies. It usually has one color on one side and a different color on the other side. Gold/silver is the most common. It really doesn't matter which brand mylar tinsel because they are all virtually, if not, the same.
You don't need to buy the pearlescent flats and ovals for classic flies. Nor do you need the prismatic plastic tinsels for classic flies.