Overall theme

One of the few premium aggro decks near the top of the meta (alongside various Avatar of Air decks, Ash Imposter, and possibly Ash Necromancer), Monofire Pathfinder (MFPF) is probably the simplest to pilot across many different matches at a basic level. The skill floor is quite low with any Pathfinder deck, since you don't play the game in a fair way, and don't have to worry so much about when to draw a site or playing the right site at the right location. That natural card advantage (almost always playing a site and drawing a card every turn) is what you should be trying to leverage when playing this deck, specifically, attempting to door your opponent quicker than they'd like, and then to finish them off with a very high density of spells that can kill them immediately.

But make no mistake: at the higher levels of play, there are a ton of decisions you have to make carefully. Pathfinder is THE deck to play if you want to "get luckier than your opponent before they do" as I like to put it when people ask me to explain this deck, but you will do better with MFPF if:

1) you have a light (or even strong!) grasp of statistical analysis, intuitively calculating your odds of pulling specific outs by a given turn and hedging your plays accordingly;

2) you understand every single two, three, or even four card combo/setup in your deck;

3) you are highly opportunistic, capable of capitalizing on new plays that open up to you the moment you flip a specific site with Pathfinder (since you never know exactly what you'll get).

Strategy

Generally, you want to play this deck aggressively, but don't get too lost in the sauce and only turn guys sideways. In fact, you should probably try to kill as many enemy minions without your minions getting killed (ie, trade up) while progressing forward in the realm towards their avatar and dealing as much damage to them as possible during that progression.

If you can't kill something without losing all your tempo, just go for damage and use your Avatar's life to soak up your opponent's actions, and race them. Since cards with Charge can be played out of sequence and still attack later in the turn, taking actions before playing a site (when you can) is pretty good for you, especially with Trinket in the mix. And generally, Charge is kind of hard to account for when the realm is so spread out (from Pathfinder being all over the place sometimes).