I made a similar article last week... though initially going 'pack only' had so much success with the untradeable gold upgrade packs I decided to go completely untradeable.
So far pulled Pogba, Hazad (NIF), Thiago Silva, Benzema, Filipe Luiz, Barzagli, Otamendi and countless others. Got pretty strong starting line ups for all the major leagues and enough players to cover pretty much any WL requirement thrown at us... Loving it to be honest.
Main reason I did it was to take the hassle of trading and constantly worrying about prices/chopping and changing my team away. Found before after a bad game I'd rage sell someone and would never be happy with my side, constantly thinking about ways it could be upgraded. And after playing FUT for three solid years always found you'd end up with the same team in the end regardless.
This has bought the fun back. Loving my untradeable Ruffier - Valencia - Varane - Filipe Luis - Pogba - Matic - Firmino - Martial - Hazard - Benzema side.
Is such a refreshing change.
At first I was just pumping in the players I had left over from gold packs but yeah, after packing Pogba and Thiago Silva in pretty much consecutive upgrade packs (cheek of some people eh? lol) I decided to just buy up a load of cheap gold players and do it that way. Is far, far cheaper.
Way I'd do it is quickly buy complete 11 man squads for each league with enough gold players on the web app for 400-450 a piece (always found it quicker that way), put all those in to the upgrade packs, open, rinse and repeat.
It's been a lengthy process but am almost out of coins now, thank God. Can actually start playing more than two games a day