Paul had Timothy circumcised because Timothy had a Jewish mother and was to accompany Paul on his travels. It was basically a way to not cause scandal to the Jews they would be preaching to, since Jews looked down on those who were not circumcised.
Paul made it clear that one does not have to be circumcised in order to be a follower of Christ because Paul made it clear that we are living under the new Covenant of Christ which is through grace and not by the Law of Moses. Paul was pretty harsh towards those Jewish Christians who said that Gentiles must be circumcised in order to be Christians.
2 Now I, Paul, say to you that if you receive circumcision, Christ will be of no advantage to you. 3 I testify again to every man who receives circumcision that he is bound to keep the whole law. 4 You are severed from Christ, you who would be justified by the law; you have fallen away from grace. 5 For through the Spirit, by faith, we wait for the hope of righteousness. 6 For in Christ Jesus neither circumcision nor uncircumcision is of any avail, but faith working through love. 7 You were running well; who hindered you from obeying the truth? 8 This persuasion is not from him who called you. 9 A little leaven leavens the whole lump. 10 I have confidence in the Lord that you will take no other view than mine; and he who is troubling you will bear his judgment, whoever he is. 11 But if I, brethren, still preach circumcision, why am I still persecuted? In that case the stumbling block of the cross[
a] has been removed. 12 I wish those who unsettle you would mutilate themselves! (Galations 2-12)
Galatians 5:2 Mark my words! I, Paul, tell you that if you let yourselves be circumcised, Christ will be of no value to you at all. (See also the cross references on that page.)
Also:
https://www.biblegateway.com/passage/?search=Galatians+3&version=RSVCE
As for Peter:
Acts 10 RSVCE - Peter and Cornelius - At Caesare (God gives Peter the vision of the unclean animals and tells him to kill and eat them. Peter refuses at first until God says that what He has made clean, you must not make unclean. Later in the chapter, Gentiles, who are uncircumcised receive the Holy Spirit and the Jewish Christians are amazed.)
As for Jesus, His ministry was primarily to the Jews so circumcision wasn't something He really focused on. However, some Gentiles did believe in Him and not once did He tell them to get circumcised (such as the case with the Roman centurion who requested that Christ heal his servant).