Apply Student X1 visa and also tourist L type at same time?

Dear All
I am from Seychelles, coming to china for study in sep this year. I have already application form and the notes from my school. What I need to do now is to go to Chinese Embassy in Seychelles to apply. My question is that my plan is to come to China in July for a month holiday. This one month before I start my school, should I apply another visa, like tourist type or I can already come with a student X type. Also, I am going to stay with a friend of me( a Chinese family during all these time, visiting time and school time both), do I need an invitation letter from them. is it necessary to provide it while applying X1 type.. Thanks very much. Regards
Kenneth