Remember to cast Experimental Synthesizer or Reckless Impulse before playing your land for the turn, unless you’re specifically trying to play around Spell Pierce or another taxing counterspell.

Great Furnace can be sacrificed to Kuldotha Rebirth like any other artifact. Sometimes it’s correct to Rebirth on turn one, especially if you have two more lands or your opponent won’t have an immediate way to deal with the pressure of three 1/1 Goblins.

Using your mana every turn is very important. It might be better to fire off a Reckless Impulse on turn two so you use all your mana instead of just casting a one-drop.

The Samurai from Experimental Synthesizer is white (and has vigilance), which is very important to remember against opposing Prismatic Strands or other ways to give protection from just one color.
Pyroblast can target any spell or permanent, not just blue ones. It won’t do anything if it’s not blue, but casting it will still trigger Prowess, which can be relevant for extra damage.

Double-check what mana your opponent could produce before casting Chain Lightning. This is most obvious against the mirror, but lots of decks you might not expect can make two red mana thanks to cards like Utopia Sprawl and Abundant Growth.

Finally, I’ve learned to not keep one-land hands at seven cards, no matter how tempting they look. The deck is much more functional with a second land on turn two and has so many ways to mitigate flooding.
Mono-Red is a great way to try out Pauper. It can struggle with opposing Blue-Black Control and certain Gates decks but has little trouble against Green-Red or Black-White midrange lists. It might be easy to pick up, but there are lots of tricky lines and interactions that will reward anyone who spends some time learning to master the Mountains!