Unpopular opinion but while Stardress is pretty I wish Lucy instead of getting Stardress simply spent her time with her spirits deepening her bond and learning their specific magics like how Duke learn Diver and simply combined the magics to develop new techniques.
Like spending time with Gemini learning transformation and copy magic and spending time with Leo learning light magic. Then eventually creating a technique combining both magics in which case she can transform herself into light which in turns allows her to make herself invisible, glamour herself, flight and enhanced speed.
I was a big fan of the spirits being Lucy's main source of power, but I think at this stage of the manga that's impossible. And the Star Dress Mix grew in my conception.
I am very much looking forward to the combination of Taurus + Cancer. If I'm not mistaken, Taurus's ax is capable of absorbing magic and releasing it. Combining this ability with Cancer's Scissors can generate a very interesting ability.
Maybe a giant Scissors capable of cutting magic? In addition, this SD Mix could grant two very relevant stats for short range: Strength and Speed.
I have a lot of bets on this Star Dress combination. For visualization purposes, I like to think of Gwen from League of Legends and Sheele from Akame Ga Kill.