I would say that the best Leader to play with junks is probably Morphun. Junks have quite a few pill manip cards, so Morph helps tear them up and leaving you with the constant advantage. As far as the structure of your deck goes, you need to tell me what mode you are considering. For extended I used to use : Rowdy , Haze , Fuzz , Onik , Gibson , Taham , Qubik and Nobodroid. So tell me what mode it is you want to play, and I will give you a deck idea.

Just use what you prefer, you have all the best cards from their clan already. So I'd suggest : Haze, Rowdy , Qubik , Taham , Fuzz , Peeler , Nobrodroid and Perhaps a Leader card. I remember I won my very first deathmatch with a Junkz deck. out of 13 games I never lost a single one. Rowdy is such a threat, because he is a good 2HKO follow up or a great bluff, since your opponent will definitely play a few pills when you pick Rowdy.

Both Hugo and Morphun are great with Junkz. If you want to play extended deff use Gil and Rowdy,
here are the cards i like best, just fit them into a deck yourself, or use other cards you like
2*: Gil, Flanagan. Veenyle Cr, Dreen
3*: Tremorh, Jiro, Lolly, Onik, Stiko
4*: Rowdy, Qubik, Gibson, Eebiza
5*: Haze, Fuzz, Peeler (for high *-count deck gamemodes), Maazk, Neil, Taham

As you see I think Junkz have lots of good options for every level, Just pick the ones you like.