It could be considered pay to win if you buy adorables and play on reaper vs someone who is free to play and only had Scally. (You might not understand this but basically adorables are so overpowered on a map called reaper that it's really hard for someone with scally or feedback to beat them.
Outwitters is fully enjoyable as a free download but if you find yourself enjoying it, it's completely worth the 10-20$ to get the uber pack.
I'll break it down the best I can from memory.
First a quick note. All of the races have the same 5 units (though they look different they all act the same.) the only difference between the races is the special unit. The 6th unit is completely unique and makes the races play very differently from one another. You might not believe that one unit can make the races play so differently from each other but I promise you the differences are huge.
You can download the game for free and that gives you access to 5 matches and the scallywags team. I would do this and play a few matches to see if you enjoy the game. It's kind of like chess but pretty different because of the races and maps and hexes.
Quite a few players have access to all the races and still prefer to play Scallywags.
You can buy individual races I think for 4.99 each but don't quote me on that.
If you want me to break down the differences between the races for you I'd be happy to. Just let me know
Now the best deal is the uber pack. The uber pack unlocks all the races. I'm not sure if it includes the second generation maps but I don't think it does.
Second gen maps are cool to have if you play a lot of friendly matches with friends but not necessary. If funds are right I'd skip this purchase. People with second gen maps can still invite you to a game if you wanted to play on them.
Base skins change the way your bases look. There are 2 skins and the standard look for each race. I'm not sure how much they cost because there have been price changes since I bought everything. It says right in the app when you click the store tab. The base skins are probably the last thing you would want to buy, only the most hardcore of outwitters fans seem to have them. I'd recommend playing the different races and seeing which one you like the most then buying one or two for that race.
If you buy anything you raise your game limit to 25 and get rid of ads. You can also purchase another 10 game slots if you are going hard on outwitters. Total 35 games. I have used all 35 slots in the past but this game is an addiction for me.
I guess if your only goal was to get rid of ads and get more game slots you could buy a single race or a skin for scallywags.
Personally I have bought everything because I'm such a huge fan. I have easily put thousands of hours in to this game. It's by far the most value I've ever got from a game, so I thought I'd support the devs as much as possible.
In order of importance, I'd recommend getting uber pack, then second gen maps if you play a lot of friendlies, or the extra game slots if you find yourself maxing out games. You can buy individual races of course instead of the uber pack but you wouldn't know which one you liked the best which is why I'd buy the uber pack if possible. The last thing to get would be skins because they add absolutely nothing except for a cool new look. Skins don't affect the game at all.
One more thing, I think you can get put in the second gen maps if you play ranked or random friendly games. I think the second gen map purchase is purely for if you want to start matches with friends and have access to start them on those maps. I'd definitely only buy the uber pack until you have enough information to decide what else you want to buy.