I am League 3 player (750 matches played with Penny) and you should consider this to be a guide for League 3-7 players.
If you are L8-L9 player, I would recommend to watch basic Penny Fox guide first.
If you are L1-L2 player most probably you will know majority of the stuff, shown here (but I still hope you will find something new interesting!).

SpaceAdmiralLaika’s twitch:
Popuptwo’s youtube channel:

If you want to learn more about Penny’s upgrades and a build for her, check out this text guide of mine:
My gameplay videos:

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