No preparation，no success. Please do enough preparation ,once everything is ready ,you can carry out your plan. It is same in the game which you like .
Once you feel you are ready give Amdapor Keep a try. The bosses in this dungeon can be tricky until you learn their patterns . You should give ourAmdapor Keep guide a read before entering. Amdapor Keep will drop ilevel 60 gear which is a nice filler until you can get the Darklight for that slot.
You are also ready to begin your relic quest. For now you can easily progress on the relic quest until Garuda. It may be worth fighting Ifrit a number of times to earn an ilevel 60 weapon . Perhaps you can gain some ffxiv gil in this game.
You should have at least ilevel 60 gear in every slot, with some 70s mixed in , before you can take on Garuda. I list all 3 because Amdapor Keep is normally the best dungeon to farm tokens, but as you are limited to 300 Mythology tokens per week it is better to switch to the story dungeons once you have reached the cap.
You should go complete that part of your relic quest once you have reached the state of readiness for Garuda. Your next goal should be obtaining a full set of Darklight armour and aprimal weapon if you do not have one yet. Have patience.
Last you have your relic you can go unlock the Binding Coil of Bahamut, which is the main end-game raid within FFXIV: ARR. In here you can get ilevel 90 Allagan equipment .You are good and come on!