Even if you don't have time to play the game, you can get the daily login rewards simply by logging in, and the rewards will get sent to your mailbox. Often times there are multiple login rewards happening at the same time, so missing a day can mean losing out on some free items/visiores.
First thing you should do are the daily missions. You need a total of 100 Progress Pts in order to get the last chest, which gives some royal rank exp, visiores, and 1 rare summon ticket.
Each daily mission gives a certain amount of Progress Pts, and completing them all gives 150 Pts, so you only need to complete some of them to get the final reward. Once you complete them all, be sure to tap the treasure chest icons to claim those rewards.
[List of Daily Missions]
Once you pick up all the treasure chests from the daily mission, be sure to also claim the daily token that's available in the "tokens" menu.
The general shop sells random shards, crafting recipes, and materials. But they usually sell shards for the currently ongoing event/banner, whether it's unit or VC.
If you want to speed up the process of raising a unit, you'll want to check the shop every now and then. It resets every 6 hours, starting at the daily server reset.
You can update the selection for free once a day by tapping a "Update" button on the bottom right corner of the shop. For additional selection updates, you will need to spend visiore.
Additionally, be sure to check out the other sections of the shops. There's almost always 1 free item available every single day, and it's always on the top left slot of certain shops.
Buying these also completes the daily mission to purchase an item at the shop.
Normal summons gives a variety of items and unit/vision shards at any rarity, so there's a small chance that it gives a UR shard of whatever unit/VC that you are trying to raise. It costs 1 million Gil in order to do 1 multi summon, but you get to do it for free 3 times a day, starting at when the server resets.
Chocobo expeditions are a main source of getting magicites, which are the items used to level up your espers, and they also have a chance to give unit shards, but only for units with the same element as the destination of your expedition. Units used to send out on an expedition gets some exp as well, so it can be another good way to level up many characters at a time.
On the Guild menu, tap "Attend" each day. You will receive rewards depending on total member attendance and Guild Statue Level.
Tap "Gifts" on the Guild menu and send/ claim gifts.
Some guilds require members to enhance a Guild Statue three times each day.
You can spend Gil, Visiore, or exclusive guild items like Serpent Venomous Fang.
In many cases, spending Visiore for enhancing statues isn't recommended, especially for beginners. To give the statues more EXPs, spending guild items is recommended. You can trade guild medals for these items at the MogShop.
By replenishing the Provisions Warehouse you can turn on the Barracks effects: Increasing Bravery, decreasing Faith and increasing the unit's JP.
Send gifts to your friends every day, then your friends also send you gifts. This is also one of the daily missions.
To avoid a gil shortage (it can happen frequently), it is recommended you clear the Gil Chamber every day. It can be completed a maximum of 3 times per day.
On Monday, the drop rate is doubled. On Saturday and Sunday, the completion cap is removed and it can be run an unlimited number of times.
Attempting Growth Egg Chamber & Pot Chamber is the main way of getting Growth Egg and Armor Pots/Burst Pots.
Guild Battles are open for 10 hours each day starting 13 hours after reset time. Some guilds require members to participate in this.
Battles are auto.
Hard Quests are quests that give unit/VC shards. You can go there by tapping on the "Hard Quest List" button in the "Story" screen.
You can get 1 Unit Shard from a Hard Quest. Each Hard Quest can be attempted 2~3 times depending on a unit's rarity, and Hard Quests in total can be attempted 10 times a day.
For example, 1 Mont Unit Shard can be obtained each time you attempt Mont's Hard Quest. Since Mont is an MR unit, you can attempt that Hard Quest 3 times a day. Mediena is UR, so that you can attempt her Hard Quest 2 times a day.
To make things easier, tap the "Edit Bookmarks" button at the top
and find the units that you want to raise by selecting "Southern Lion's Valley" or "Glacial Lands" and click "Save" once you're done.
In the "Bookmark" tab, you can tick the checkmark on each unit so you can use the "Skip All" button at the bottom right to automatically do all of them.
Additionally, you can also do this with Vision Cards. Simply select the Vision Card tab at the top and do the same as before.
The main difference between the unit and vision card hard quests is that you can only do each vision card once, and a total of 6 attempts per day.
Doing all unit and VC hard quests will require a total of 320 NRG.