As a Catholic, am I obliged to believe in visions and saints? I am a Catholic.

There are many visions and ecstasy and saints.

As a Catholic, am I obliged to believe in visions and saints?
The Church distinguishes between two ways God has spoken to the world: the "public revelation" beginning with the Old Testament prophets and culminating in the life of Jesus, and the "private revelations" of miracles, visions, etc., which have been given to various individuals throughout history since then.  

You are only obliged to believe in the public revelation.  CCC paragraphs 65-66 read:


  65 "In many and various ways God spoke of old to our fathers by the
  prophets, but in these last days he has spoken to us by a Son."
  Christ, the Son of God made man, is the Father's one, perfect and
  unsurpassable Word. In him he has said everything; there will be no
  other word than this one. St. John of the Cross, among others,
  commented strikingly on Hebrews 1:1-2:
  
  
    In giving us his Son, his only Word (for he possesses no other), he
    spoke everything to us at once in this sole Word - and he has no more
    to say. . . because what he spoke before to the prophets in parts, he
    has now spoken all at once by giving us the All Who is His Son. Any
    person questioning God or desiring some vision or revelation would be
    guilty not only of foolish behavior but also of offending him, by not
    fixing his eyes entirely upon Christ and by living with the desire for
    some other novelty. There will be no further Revelation
  
  
  66 "The Christian economy, therefore, since it is the new and
  definitive Covenant, will never pass away; and no new public
  revelation is to be expected before the glorious manifestation of our
  Lord Jesus Christ." Yet even if Revelation is already complete, it
  has not been made completely explicit; it remains for Christian faith
  gradually to grasp its full significance over the course of the
  centuries.


So not only are you not required to believe in any subsequent visions, you are warned not to go looking for them out of a desire for novelty.  Since revelation is already complete, then any new (apparent) revelation that contradicts prior teachings is certainly false.

However...


  67 Throughout the ages, there have been so-called "private"
  revelations, some of which have been recognized by the authority of
  the Church. They do not belong, however, to the deposit of faith. It
  is not their role to improve or complete Christ's definitive
  Revelation, but to help live more fully by it in a certain period of
  history. Guided by the Magisterium of the Church, the sensus fidelium
  knows how to discern and welcome in these revelations whatever
  constitutes an authentic call of Christ or his saints to the Church.


Some of the claims of miracles, apparitions of Mary, and the like, are almost certainly true.  Guadalupe, Lourdes, and Fatima come to mind.  None of these were sent to change the faith or add new teachings, but each did serve an important role at a certain place and time in history. (Guadalupe, for example, was very important in converting the New World to Christianity.)  

There are probably also many claims of miracles and visions that are exaggerated or false.  Even some of the saints may be little more than legends.  You are free to decide for yourself which of those claims are credible and which are not.

The bottom line, though, is that none of these "private revelations" actually change the teachings of the church, so whether you accept them or not, your faith still rests firmly on the teachings given to the Apostles by Jesus in the first century, and no "update" is expected until He comes again.