Theme team no money spent worth it?

I play a lot online H2H and like the idea of a theme team. But isn’t way more expensive in coin to do so? I want to still be competitive online and not be at big disadvantage or pay twice as much just to have a theme team. 
 

Also can my theme team be like all legends or doesn’t have to be the same team in order to get the bonuses? 

isn’t best to do 20/20 or all players from same team?

please help.

i run 20/20/20 49ers/commies/cowboys nms, team was maybe 1M coins total. got champ 3 last ranked. just build around your good BND cards

its cheaper to do because you arent chasing every new shiny card and are only getting the ones that fit your theme team(s). plus the boosts make cards stay relevant longer. there is no legends theme team this year. needs to be players who played for the same team at any point in time. for example I was just 20/20 bucs, 49ers, and cowboys, but im about to switch to 40/40 bucs and 20/20 niners because they upped the theme team boosts. ill be getting +2 speed (and other stuff) on all of my bucs players and +1 speed (and other stuff) on all my niners players. plus if you level up team captains enough you can get up to 3 different team chems on one player. you can use the team builder on here to play around with lineups and cook something up.