I will not buy a switch -> Je n'achèterai pas de Switch
You can also say "Je ne vais pas acheter une Switch". The two sentences differ a little bit, the first one is better as it means "I do not intend to buy a Switch in the foreseeable future", it is like a "general truth". You can use the second one in a context where you say what you will do or not do this afternoon for example : "Je vais faire les courses, j'en profiterai pour acheter une switch, et... attend, j'ai plus d'argent. Bon, je ne vais pas acheter une switch."
Just in case :
I will never buy a swich -> Je n'achèterai jamais de Switch
(you can't say "je ne vais jamais acheter de switch")