Family First Prevention Services Act of 2017 This bill amends part E (Foster Care and Adoption Assistance) of title IV of the Social Security Act (SSAct) regarding, among other matters: (1) mental health and substance abuse prevention and treatment services and in-home parenting skill-based programs, (2) foster care maintenance payments for children with parents in a licensed residential family-based treatment facility for substance abuse, and (3) payments for evidence-based kinship navigator programs. Part B of title IV (Child and Family Services) of the SSAct is amended regarding, among other matters: (1) time limits for family reunification services for children in foster care or returning home, (2) grants for the development of an electronic interstate case-processing system to expedite the interstate placement of children in foster care or guardianship or for adoption, and (3) targeted grants to increase the well-being of children affected by substance abuse. The bill appropriates certain funding to Department of Health and Human Services for FY2018 for competitive grants to states, Indian tribes, or tribal consortia to support the recruitment and retention of high-quality foster families. The bill amends part B of title IV of the SSAct to reauthorize through FY2021: (1) the Stephanie Tubbs Jones Child Welfare Services Program, (2) promotion of safe and stable families program, (3) funding reservations for monthly caseworker visits and regional partnership grants, and (4) funding for state courts. Part E of title IV of the SSAct is amended to: (1) revise the John H. Chaffee Foster Care Independence Program and related provisions, and (2) reauthorize adoption and legal guardianship incentive programs through FY2021. The Government Accountability Office shall study the extent to which states comply with certain SSAct requirements relating to the effects of phasing out the Aid to Families with Dependent Children program income eligibility requirements for adoption assistance payments.