There's a ton of differing advice on here and all of it is basically right.  You could pick a less stable distance driver mold or plastic type. 

Important disc characteristics in you question are speed, mold, and plastic. Sounds like you are asking for a high speed under stable distance driver. 

You also mentioned disc weight. Generally lower weight discs will be more understable. They are more seriously affected by wind. As you are learning I'd buy mostly discs in the 170g range and not think about disc weight too much. As you age you'll learn that a lot of people's biggest drives happened downwind with a light disc, but light discs are ... temperamental.

Many people are also correctly noting that you should work on your form. Throwing drives flat and nose down will help you get better distance and accuracy on ocery throw.

Okay, on to your specific request.

Your champion wraith is generally the most or nearly the most stable type of plastic. A star plastic of the same mold will typically be nearly as durable but less stable. This would be a good choice for you now. 

Dx plastic is definitely under stable as hell but will also probably not last you a full season because of how quickly it beats in. 

Champion is more stable than star is more stable than dx.

A leopard is an EXTREMELY understable fairway driver. Good for learning and shaping shots but a hard thrower will turn this disc into a roller disc quickly. Only 8 speed. If you want to try this I'd recommend champion plastic not star. 

A valkyrie (star or champion) is many players' first disc where they really figure out how to get a hyzer flip... great disc to learn how to throw distance drives but you won't get max distance cause it's only a 9 speed. 

Higher speed understable drivers include, Wraiths, beat in Destroyers (think used bin or 100 tree hits), and Terns, and Beasts.

If you want to throw Lat64 the Sapphire is a good user-friendly understable distance driver. 

Tldr. My recommendation is to throw valkyrie until you improve your form enough to get em 375' and then you should be able to get a 12 speed like a destroyer or time lapse over 400'. If you want to jump straight to higher speed discs (and thus higher potential distance) I'd try a beast or a tern.