it is also good idea to try a few games in a free mode and create a strategy. Then to apply it with real bets. It can be done on Fairspin without any problem
free mode is not just in your casino but in all casinos and free mode is only for playing when the player doesn't have the funds or doesn't want to risk the funds, and I never thought there was a strategy in slots only usually players will increase the bet amount when they feel they will get win even though the chances of getting it wrong are as big as getting it right.
Sadly there is some strategy in slots but it isn't about how to win in a bet in slot game but rather an approach to what slots to choose. The number of spins before giving up. So the strategy isn't limited to wagering method like martingale and alike, strategy also applies to the kind of engagement a player will do. Oh and understanding how a slot works is also a kind of strategy.