@mikebelyaev You can use "ti credo", but it means "I believe you", "credo in te" is "I believe in you". "Ti" often is in front "ti credo, ti voglio, ti amo, ti desidero, ti cerco, ti dico, ti scrivo and so on" (I believe you, I want you, I love you, I wish you, I look for you, I say to you, I write you)... "te" never is in front (Io credo a te, Io voglio te, Io amo te, Io desidero te, Io cerco te, Io dico a te, Io scrivo a te). What I'm saying is just a simple way to understand "ti" and "te", but it doesn't explain everything, for that you need an Italian grammar, mine is just a little trick, but I perfectly know that not always it works. The gender doesn't matter ”ti, te" is "him, her", the context would explain to whom.
The personal pronouns are I, you, he, she, it, we, you, they (io, tu, lei, lui, noi, voi, loro)
clitic pronouns or object pronouns can be divided into indirect object (clitic) pronouns and direct object (clitic) pronouns.
The object pronouns are very difficult for English speaking people. Which pronoun you have to use doesn't depend on its function in the sentence (main object or not) it depends only on the grammatical case which has to be applied (accusative or dative). The direct object pronoun is used with the accusative and the indirect object pronoun with the dative.
direct objects stand directly after the verb (dire qualcosa)... In English you ask for them with: what or whom (and the answer is really him or her etc.).
indirect objects take a preposition between the verb and the object (dire a qualcuno) ... In English you ask for them with: to whom, to what, for whom, for what... (and the answer is to him, to her, etc.)
Sometimes English and Italian verbs used different object pronouns:
i.e. to phone:
to phone someone (whom do you phone?) = direct object pronoun
telefonare a qualcuno = indirect object pronoun
Unfortunately the best way is to learn verbs directly with the corresponding objects ("telefonare a qualcuno", mandare qualcosa a qualcuno etc.)
The object pronouns themselves can be divided not only in direct and indirect pronouns but also in tonic (accented) and atonic (unaccented) pronouns.
a) accented direct pronouns:
me, te, lui/ lei/ Lei, noi, voi/ Voi, loro b) unaccented direct pronouns:
mi, ti, lo/ la/ La, ci, vi/ Vi, li/ le d) accented indirect pronouns:
a me, a te, a lui/ a lei/a Lei, a noi, a voi/ a Voi, a loro e) unaccented indirect pronouns:
mi, ti, gli/ le/ Le, ci, vi/ Vi, loro
You can also have a look here:
No, if you use a preposition you have to use the tonic object pronoun.
"ti credo" exists but comes from the word "credere a qualcuno" "Ti credo" means: I believe you.
To see more about tonic and atonic object pronouns and its use have a look here: