Me, us, home
Beyond watashi: boku, the softer male 'I' that works casually and with desu/masu, -tachi for 'we' and 'X and the others', and uchi for home and 'our side'.
boku
polite watashiI, me (male, casual)
僕 ぼく 私
The softer male 'I': gentle among friends (ore is the rougher, very common one there) and still fine with desu/masu among coworkers. Women don't use it, and with strangers, clients and superiors watashi is the safe choice, so the polite form here is watashi.
boku mo sou omou.
I think so too.
僕もそう思う。
watashi mo sou omoimasu.
I think so too.
私もそう思います。
ore is the rougher male 'I' among friends: learn to recognise it and save it until you know the group. Adults also call a small boy boku (boku, namae wa? = what's your name?), so there it means 'you'.
Learn first: watashi
-tachi
and others; plural (people)
〜たち たち
Attaches to a person word or a name to mean that person and their group: watashitachi (we), kodomotachi (the kids), tanaka-san-tachi (Tanaka and the others). It is used for people (and pets), never for things.
tanaka-san-tachi wa mou kaetta yo.
Tanaka and the others already went home.
田中さんたちはもう帰ったよ。
tanaka-san-tachi wa mou kaerimashita yo.
Tanaka and the others already went home.
田中さんたちはもう帰りましたよ。
Men also say bokutachi or bokura, and oretachi or orera (rougher, common among male friends). Plural is optional: kodomo alone can already mean 'the kids', so add -tachi when you want to stress the group.
uchi
home; our (family, company)
うち
Means home, usually your own (uchi ni iru, uchi ni kaeru), and uchi no puts the next noun on your side: uchi no kaisha (our company), uchi no ko (my kid).
kyou, uchi kuru?
Want to come over to my place today?
今日、うち来る？
kyou, uchi ni kimasen ka?
Would you like to come over to my place today?
今日、うちに来ませんか？
ie means the house as a building. As 'I', uchi is Kansai or young women's speech, so just recognise it.