Yeah, youll be swimming in tomestones soon enough. Every level 50 dungeon raid and trial gives you some, the first time you do most of said dungeons trials and raids you get a bonus of a bunch extra, most of the roulettes give you more, then once you get to 60 the dungeons raids and trials will give more, the first time bonuses will be even more, and thats on top of other methods you could acquire them. As was mentioned, most beast tribes offer a small few of them for doing their daily quests, you can find them inside some chests if you get a map and go treasure hunting, and a couple other methods too.
To the original questions, dont worry too much about gear yet. The way the game is set up, gear levels slowly increase as you level up. Then when you get to a cap level(50, 60, 70 for ARR, HW, and SB respectively) they shoot up by a great deal(at the end of the HW story you likely have an ilvl approaching 150, by the beginning of the stormblood story its jumped all the way close to 260 - then going through the stormblood story gets you to roughly 290... we'll see how high we get before they get to 5.0). Safest course of action is to do your quests, and buy upgrades with tomes as you can afford them at the cap levels(tome gear will be basically the best at cap levels), and keep an eye on dungeon drops to see if its better or worse then what you already have. And if you feel like your gear is sub-par, the most important piece to upgrade is your weapon. It makes the biggest difference in your performance.
As for glamours, do the level 50 quest in Revenants Toll to unlock the system. Crafters can make glamour prisms at level 30(though you need to level one up to 50 to get the recipes), but you can also buy them from people off the market board. Either use the cast glamour ability from the menu, or right click the item you want to change and cast glamour. Itll show you the options you have on hand(it doesnt check retainer inventory), and what kind of prism is needed(for instance to make a robe appear to be a leather armor you probly need a leather prism). You can only apply glamours that can be equipped by the class on the gear(so no making your BLM robe look like a dragoon only set of mail), and you cant make something appear to be higher level then it is(no putting a level 300 glamour on a level 50 armor - the game has several sets of glamour only gear and all are level 1 and so can be applied to anything). Also, you can only use originals to make glamours(in other words, keep the good looking items stashed somewhere if you think you might want to use them again, a duplicate will not suffice). Once the glamour is cast, for all intents and purposes that is the new appearance of that gear, and every time you put it on it will appear as such. You can use a glamour dispeller to remove a glamour from an item, which is required if you decide you want to do a new glamour instead. So real world example. You find a robe you like the look of. You get an upgrade you dont like, and glamour the old robe on top of it. Now you have new stats with the old appearance. Later on you get another ugly upgrade, you can glamour the new one to look like the original too. Later you find a new look you like but with either bad or no stats, you can either replace the glamour on what youre already wearing(via a dispell and a new cast) or wait for your next upgrade to come along and put the new look on the new gear.