I m 19 yr old....m 5.8in height....and m nly 39 kg....i wnt 2 gain weight......nd become fat too....plz sujjes?

plz sujjest some some natural remidies...........i came 4m a middle class family..so sujjest me sumthng dat cmes in my budget..........plzplzplz i need ur hlp........