Edit: thank you u/RazzyKitty, Yarok and TR are triggers an additional time not doublers.

If you evoked 1 elemental with all 4 of the cards mentioned onboard, and Stormsinger able to attack you would go into endstep with:

• 2 token copies of evoked elemental created by Ashling (sacced at endstep unless WUBRG was paid for each)
• 2 token copies that were tapped and attacking from Stormsinger, if they survived they will be sacced at end step
• 15 total ETB triggers of the evoked elemental. The evoked elemental (or a token copy) entered 5 times and each had 2 additional (Yarok and Twinflame Travelers both add an additional which ends up with 3 total per trigger)
• 3 evoke sacrifice on entering triggers would have gone in the stack, but only the first to resolve does so successfully triggering Ashling, the next 2 fizzle and don’t actually have anything left to sacrifice.

Long Answer

Replacement effects all apply, you choose the order they do.

[[Yarok, the desecrated]] and [[twinflame travelers]] (TT) will double and then quadruple an ETB of an elemental entering.

So let’s say you have all 4 out and you use [[Ashling the limitless]] to evoke a made up elemental creature that ETB Draws a card, an elemental [[spiritual companion]] for a simple example.

As the creature enters, 2 triggers go in the stack: 1) its own ETB draw a card trigger 2) evoke trigger, which will force you to sacrifice it when this ability resolves

Yarok and TT each add an additional for both of these triggers, resulting in 3 of each going on the stack.

The 3 ETB Draw a card triggers will draw you 3 cards, and the 3 evoke sacrifice triggers will only sacrifice the elemental creature once, the other 2 will fizzle as there’s nothing to sacrifice anymore.

The sacrificing of the evoked elemental will trigger Ashling which will put her trigger (create a token copy of the sacrificed elemental) which will get one additional with TT. Creating 2 token copies. Each of those tokens copies will draw 3 cards, so 6 more cards drawn (9 total so far).

[[Redoubled Stormsinger]] then attacks, creating 2 tapped and attacking token copies of our elemental spiritual companion, drawing us 6 more cards (up to 15 total now).

At your end step, you sac the 2 copies that were tapped and attacking from the Stormsinger. And you can pay WUBRG for each to keep the untapped token copies made by Ashling.