it depends man , if you don't have sufficient tokens then its wise enough to build strong starting line up and try to go as far as you can .
if u have 100 odd tokens and you buy smartly then u can have decent overall squad depth which gives you freedom to make experiments and adjust according to opponent team's tactics

in pro football not many teams make changes to their starting line up often , yes they make some tactical tweaks here and there against some seriously strong teams at max