"Varje gång jag springer till bussen" means "every time i run to the bus". However, the sentence is supposed to be structured "Varje gång springer jag till bussen". If you write "Varje gång jag springer till bussen" it sounds as if there is to be an explanation of what you do every time you run to the bus, such as "Varje gång jag springer till bussen så ramlar jag"
"Varje dag springer jag till bussen" means "Every day i run to the bus"
The difference here is therefor that the first sentence explains what happens on every occasion, while the second sentence explains what happens daily