At one time the max was 60. In 2015 mod 6 that all changed and the max level was raised to 70, and the entire world changed. This may help explain for you why there seems to be such a difference between levels 0-59 and 60-70.
You may find that most of the focus in Neverwinter is on the max level. In fact most suggest that until a player reaches level 70 that significant pieces of the game remain untouched. This is fairly decent advice.
There is a significant amount of theme material in the game from 0-59 that lets you enjoy the game and become familiar with its mechanics and loot systems. Nearly all the equipment, currency, usable powers, relative dungeon difficulty, and player priorities change after max level is achieved.
Here are some observations about leveling in the game:
Should you buy any? Very little.
Very few items will remain the same after you hit max level. Perhaps only the artifact you chose in the early quests will remain. Everything else will have significantly better choices available to you. Though it is cheap to buy on the AH if you want to optimize a little bit, you can't get great stuff, AD is hard to get <70 level, and drops are plentiful.
What to wear to speed up levelling?
There are azure enchantments that have an experience boost. Wear these in all your utility slots.
There are also shirt/pant items that can be purchased for zen. This is not a good value and they are NOT recommended. Following these tips you can be max level in a few days, definitely less than a week. At that point your pricey exp boosting clothes will be completely useless.
Are there any events that help levelling?
There are 2 main ones. There are occasional 2x experience events. They are usually announced on the calendar (ctrl-L , change to calendar tab, change to the 'upcoming' tab).
Neverwinter siege is another event that can help. At one time it offered a massive boost. That has been reduced but it you can still get a lot of additional experience for fighting here.
Are there any locations that boost experience?
Neverwinter Siege is a place on the map, so that technically fits. The guild SH area has a similar boost as well. One bonus here is that you can be in a group, sitting in the castle doing nothing while your group gathers experience for you. Any fighting you do manage has boosted experience here as well.
The mount system got a significant upgrade in mod 9. Before that you could only use 1 mount, and only had storage for that 1, although you could buy multiples often at significant cost. This meant that valuable mounts might have to be sacrificed or they would take up a piece of inventory space which is also at a premium in Neverwinter.
After the upgrade however a 'stable' was implemented, along with all the other upgrades.This allows you to keep your old mounts, even when not using them. I have found this to be useful for storing spare insignias as I come across them. Insignias have a partially built refinement system visible to players, that has yet to be implemented. If/when that hits old unused insignias may become useful in the way lower ranked enchantments are today.
A fast mount is an unsung hero of leveling. Most lvl 70s have gotten 110% mounts, and its good to keep up with them when being taken around for stronghold heroic encounters (SHEs) to gain experience. This should be your first high end purchase. It will shorten the idle time of riding between quests, let you keep up with guild mates, and speed exiting of areas if you don't have VIP travel benefits.
VIP is another benefit that should be considered while leveling. The travel benefits will speed your access to areas, and that lets you accomplish quests significantly faster. Some of the areas take 3-4 minutes to ride into, and without VIP you will have to ride back out again. A cheaper alternative solution is to buy [Teleport Scroll - Moonstone Mask] scrolls from the auction house (AH) or win them from the Coins of Waukeen event.
You may even consider using the AD exchange to get Zen and purchase your vip subscription with that. This lets players achieve this without spending any real world money.
Starting at the first level of VIP there is a 10% experience boost here.
Don't worry about gaining Astral Diamonds (AD) until after you hit level 70. All sources of AD available to those below 70 are significantly diminished. What you accomplish after 70 will quickly overshadow everything you worked at before that.
Nothing needs to be purchased for gear before this. All the dungeons and quests are possible using gear gained from drops or quests. This isn't meaning you have to be a 'leet' player to do this either. VIP may be one exception you might wish to make here.
The major quest lines will level you up to at or near 70 by the time you get through all the available content. The devs have changed the flow of the quests over the past several mods to streamlined, but they mostly just changed the order they come in, not what is available.
The maze engine campaign quest line has large experience rewards for those after level 60, as do many pieces of the elemental evil questline. Of particular interest in the elemental evil set will be the daily Seed quests available from the druidesse below the tree in PE (protector's enclave).
Quite a few, though not all, of the dungeons available early on continue to be used as 'epic' versions after level 70. Do the dungeons and skirmishes as they become available to you. Some of them are just fun, and some of them will help familiarize you with content for later use.
Dont become comfortable with your power level in these dungeons though. It can come as quite a shock that the well-equipped ~60 lvl character goes from mashing all available dungeons to being one-shot killed in the epic versions.
The style of game-play in the epic version is completely different. One of the best skills to practice in lower level content is the ability to dodge the red and not be hit at all even though you can handle it. All but the tankiest players will be wiped out after hitting lvl 70 and need to relearn how they play. May as well start early.