public OnPlayerRequestSpawn(playerid) {
    // Is he trying to spawn with skin id 0?
    if(GetPlayerSkin(playerid) == 0) {
        // Is his score less than 50?
        if(GetPlayerScore(playerid) < 50) {
            SendClientMessage(playerid, COLOR_WHITE, 'You need a higher score than 50 to spawn with this skin!');
            return 0;
        }
    }
}

if(GetPlayerScore(playerid) <= 50) return SendClientMessage(playerid, 0xff0000ff, "You don't have 50 points in your score);