95 Dodge Neon PLEASE HELP!

July 6 has been one of the worst days ever for me, turns out I purchased this 95 dodge neon a month ago because I just couldnt deal with taking the bus and depending on people anymore. I purchased the car with 114,000 miles on it from a guy who owns his own dealership. Anyways ever since I got it I have been discovering things about the car almost everyday, like how the radio stops when u pass a bump or the engine needs like 3 minutes to be ready for the needle to be a little be up from the c mark on the temperature. Ok all of that I kind of got used to it. Then I discorvered that the AC was just blowing hot air, that I didnt wanted to take anymore specially with summer just begining. So I have been reading some posts online and I decided a week ago to go to an auto parts store to buy that Do it yourself ac kit they sell for abt $40 bucks. Ok since this was my first car the guy trying to help came out to my car to put the kit on, but he warned me that if there was a leak I had to pay for it anyways and take it to a mechanic, all of that was chinese to me so I was like ok, I just wanted my ac on. So turns out it didnt work and I paid for it and left with no ac. What a dissapoint but at least I knew what the problem was. Ok so me and my mother went to this mechanic recomended to us by her friend, he checked the car for about 45 minutes then he said that the compressor needed to be replaced as well as the hose, but that he will used that freon gas I bought so everything will cost about $275. Ok today around 9am I dropped off the neon, around 1:30 he called that the car was ready, I got there and there was a problem, he was like the pressure on the compressor made the something pop off and we had to solder it together from one side, and now the other side poped off, again all chinese to me, so he was like come back in 20 min, I returned at 4 and the car was on and ready, yet I noticed all of the smoke coming from the back, I imediatly asked what that was, he was like since the ac is on the smoke is coming out because of the pressure of the ac, I was like what it never smoked like that before then he said that I also needed a new battery because the car need to be jumped start, because my battery was too old and since the ac was on it has used most of it, oook, so he was like take it to that auto parts place they replace it for u just dont turn the car off, I was like u know what I am going to go buy the battery and I will come back so that you can put it in. OK so I went and got it they replaced it for me right away, the car turned on as well as the smoke, white smoke coming from the back, I mean the ac is like ice cold but the last thing I need is for me to be driving it with all of this smoke coming out, so I was not happy at all, that never happen to me since I got the car, and then he was like is prob burning oil, I was like oook I never seemed like it did, so he checked the oil and was like it seemed cleaned like it was just replaced, so I was like yeah I noticed that, then he was like you should buy this LUCA liquid to clean it up, then the smoke should be less. Anyways at that point I just wanted to leave, so everything came to $300 and the white smoke that I dont know how to fix, I just really wanted the ac ready for the summer. I need help, what is that white smoke? Does it ever stops with the ac on?