Since it's an instant, you simply pass your turn, wait until your opponent's upkeep, and then cast it, which is very close to getting an extra turn (the main difference is that your opponent will get to untap)
A Flash Subtheme Beyond Alela encouraging you to keep attacking, the card also incentivizes you to cast lots of spells at Instant speed
There just arent a lot of Supporters that increase damage, so being able to add on an extra 20 damage is quite useful, especially for decks like Night March and Vespiquen/Flareon that often need just a little something extra to knock out a big Mega, and then being able to refill your hand is just icing on the Poke-cake
One could look to add some extra counter multipliers as easy upgrades
Trust your gut, but always check the facts.
I think that where Surging Sparks really shines is in its super well rounded roster of Pokmon included within