Learn Spanish (Latin America): Mi futuro depende de ti.

In English, we say 'depend on', but in Spanish, the verb depender is always paired with the preposition de (which usually means 'of' or 'from'). This is a fixed verb-preposition combination you just have to memorize, much like soñar con (to dream about). Never say depender en!

Why is it ti and not tú at the end of the sentence?

Because the pronoun comes right after a preposition (de). In Spanish, when a pronoun follows a preposition, it often changes its form. For the informal 'you', the normal subject word is tú, but after a preposition, it changes to ti.

Does the word ti ever need an accent mark?

No, ti never takes an accent mark. While mí (me) needs an accent to distinguish it from mi (my), there is no other word spelled 'ti' in Spanish. Therefore, it doesn't need an accent to tell it apart from anything else.

Why does the verb end in 'e' (depende) if the sentence is about 'my' future?