The quote from Luke 6:35--"But love your enemies, do good to them without expecting to get anything back. Then your reward will be great and you will be children of the Most High, because he is kind to the ungrateful and wicked"--represents a major tenet of the teachings of Jesus Christ. In his teachings, Jesus sought to elevate man to a higher moral plane, and a central component of this was the idea of resisting the almost-primal urge to confront evil with evil. In both the above quote from Luke and in an earlier passage from the Book of Matthew, a passage associated with the Sermon on the Mount, Jesus sought to teach mankind of the perils of temptation, in this case the temptation to exact revenge for a perceived misdeed. Anybody, Jesus argued, could lower oneself to the level of those who do evil; those destined for a sense of immortality would be those who learned to turn away from evil and to pursue the higher path. Note in the following passage from Matthew 5:7 Jesus's admonition against lowering oneself to the levels of others while converting evil deeds to positive outcomes through sheer magnanimity of spirit:

“You have heard that it was said, ‘Eye for eye, and tooth for tooth.’ But I tell you, do not resist an evil person. If anyone slaps you on the right cheek, turn to them the other cheek also.  And if anyone wants to sue you and take your shirt, hand over your coat as well.  If anyone forces you to go one mile, go with them two miles.  Give to the one who asks you, and do not turn away from the one who wants to borrow from you." 

"Love your enemies as yourself" was Jesus's mantra, and the New Testament is replete with examples of Jesus and his followers' determination to show compassion where others looked away and to forgive those who do harm as the road to righteousness. As Jesus continued his sermon, he repeatedly emphasized the expectation that personal redemption and pursuit of the higher ground were integral to the path on which he hoped to lead much of humanity. Soon after the above passage from Matthew, he added the following: "Blessed are the peacemakers, for they will be called children of God." Jesus was not about the use of violence to defeat evil; to Jesus, the use of violence under any circumstances represented a failure of humanity to follow in the path of God. The most exalted, he suggested, were those who eschewed the more violent or confrontational path and instead sought to pacify the violence that infected the souls of too many people.

In order to understand this, you should look at the context in which it is given.  This is part of Jesus’ “Sermon on the Mount” in which he is introducing people to a set of ethical ideas that might be foreign to them.  He is trying to get them to see that it is more important to be morally good than to be powerful and it is more important to treat others well than to demand things for yourself.

In this context, we can see that Jesus is telling people, in Luke 6:35, to act in ways that they would not have expected to act.  He is saying that they should be good to their enemies and should not expect to be paid back for loans.  He says that this will make God think better of them. 

The reason for this, he says, is that this is how God is.  God, Luke says, loves even the bad people.  He loves the ungrateful and the wicked.  Therefore, we should be like God.  We should also love bad people.

So, Luke is not saying that we will be wicked and ungrateful and therefore God will love us.  Instead, he is saying that if we love people who are wicked and ungrateful, we will be acting like God and that is a good thing.