The right time to start seedlings

[THM_18]

Hello everyone,

I'm starting to plan my veggie and herb garden. I'm going to grow basil, cucumber, pumpkin, spinach and tomatos. I modified a egg carton for my seedlings. (See pic attached) I'm going to start them inside because freezes are still regular. I would like to know when I should start them, I'm was planning to start them this week, but I understand some seeds might need more or less time before their ready to get planted. Also, does anyone know where I can find out how many square feet I'll need for each plant?

Thanks for the advise,

THM_18