Let say you do bosses, you can make 600k in 4 hours, a 15 days ms. Next week do Battle Bot and do it 3 times, you will get a free ms extension. Just keep grinding game and you will be able to pay a ms without putting a single Dollar in game.
My question coming in my mind is : why you buy evolution items such as stone to player when you can buy them in a dept. Store? Let say you have a lot of ressources such as a Frisk pokemon and a Thief pokemon, getting items are easy.
You can try to farm PvE coins and buy cosmetics/mounts without spending pokedollars but it's not for newbie player. Such as every game, postgame exist and it's supposed to be rewarding.