Also:

1) jouer AU basket

2) déjeuner: if used as a noun, you would rather say: PRENDRE MON déjeuner / PRENDRE MON petit-déjeuner instead of manger.

Aujourd'hui j'ai décidé d'écrire un peu en français.

Ce matin, je me suis levé et je suis allé me brosser les dents et prendre un bain. Puis, j'ai déjeuné. Après, je suis allé dehors pour jouer basket avec mes amis. Je sais que nous sommes en décembre, mais où j'habite il n'y a pas neige jusqu'en janvier. Après ça, je suis allé à la maison de mon ami et nous avons joué aux jeux videos.

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That's great, it's pretty much the same mistake with conjugation. When talking about an action you did recently, you'll mostly use what we call "Passé Composé" (litteraly Composed Past). So, to say "I went to my friend's house" or "I got up" or "I had breakfast", you use this.

"Je mangeai" and "nous jouâmes" are in the tense called "passé simple". To be honest, no one will ever use this while talking, that's why I changed it. It's a fancy one you might encounter in novels more. Re-reading, I think it's what you tried to use all along? 

Last thing is the lunch thing. "to have breakfast" or "to have lunch" are verbs in french. I realise now I changed it to "déjeuner" but it's a tricky one. Breakfast in France would be "petit déjeuner", as opposed to Quebec for example, where it's "déjeuner". "Petit déjeuner" isn't a verb though, in that case you'd say "J'ai pris un petit déjeuner". I'm sorry, it's a bit confusing as this is a distinct cultural difference.