I know all characters get one action and one bonus action, but say I want to use misty step (via the Eladrin's Fey Step racial feature) and follow through with my dual swords. I know that misty step is a bonus action, Attack 1 is an action, and Attack 2 is a bonus action (I think). I also know that you can move up to 5 feet as a free (non-normal/bonus) action. At higher levels are there any feats, or are there any magical items that give you another action or another bonus action?
The rules for bonus actions state:
You can take a bonus action only when a special ability, spell, or other feature of the game states that you can do something as a bonus action. You otherwise don't have a bonus action to take. You can take only one bonus action on your turn, so you must choose which bonus action to use when you have more than one available.
You don't have a bonus action unless a partiuclar ability gives you one. So even if you have multiple bonus action abilities at your disposal, you may only use one. To my knowledge, there is no item, ability, or otherwise that can give you a second bonus action on a turn.
On your turn, you can move a distance up to your speed and take one action.
The fighter class's second level ability action surge grants an additional action:
On your turn, you can take one additional action.
The 3rd level spell haste grants an additional action:
it gains an additional action on each of its turns. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action.
Putting it all together
Now, in your question you describe using misty step and following up with your dual swords. This does not work with two-weapon fighting which states:
When you take the Attack action and attack with a light melee weapon that you're holding in one hand, you can use a bonus action to attack with a different light melee weapon that you're holding in the other hand.
If you have used misty step already, you cannot use the bonus action attack from two-weapon fighting. In order to follow up with your two attacks, you would have to have either the extra attack class feature, such as from being a 5th-level fighter:
you can attack twice, instead of once, whenever you take the Attack action on your turn.
This allows you to make two attacks with your Attack action, or you must have gained an additional action from another source, such as action surge or haste described above.
A thief rogue gets, at level 17, an extra turn in the first round of every combat. This is at the same level that spellcasters get Time Stop, but it comes with none of that spell's restrictions and takes no resources to use. A level 17 eladrin thief, for example, could use a bonus action to misty step to an opponent's location and take the Attack action, potentially adding sneak attack damage, then take another Attack action on their second turn potentially adding more sneak attack damage, then take a bonus action to disengage and move up to their movement away.
Additionally, the level 13 thief ability, Use Magic Device, allows a thief to make use of spell scrolls, staves, and wands. While a scroll of time stop-- a legendary consumable item-- is not exactly the sort of thing one wastes for merely an ordinary, if more effective, combat round, it nonetheless does grant the caster 1d4+1 additional turns effective immediately, which is at least good enough to get an extra bonus action-- if you use up your bonus action before casting Time Stop you can have another one as long as you break Time Stop with your action on a turn you haven't used your bonus action yet.
The Haste spell comes at a much lower level of scroll rarity-- 3-- but you could also just have the party mage (or, more likely, their Glyph of Warding) cast Haste on you since it's not a self-only type of thing and it's not super difficult and/or costly to Glyph like 9th level spells are. It's also available from magic items like the Potion of Speed. Regardless of the source, it gives you an extra action you can use to make a single weapon attack.
There are also spells that involve making multiple attacks, although none of them work very well with the handicap of using two swords.
Beyond those thief-specific abilities, there's also multiclassing into Fighter for Action Surge and/or Extra Attack, as well as companion-dependent options like the Battlemaster's Commander's Strike.
Reading into what you're going for:
I want to use misty step (As an Eladrin) and follow through with my dual swords.
It sounds as though Eldritch Knight would suit your purposes, although that does mean sinking 15 levels into fighter, and that might be unsuitable for the build you're going for besides what I've quoted above, since you're not really much of a rogue anymore at that point.
Eldritch Knights get a feature at 15th level called Arcane Charge (p. 75):
At 15th level, you gain the ability to teleport up to 30 feet to an unoccupied space you can see when you use your Action Surge. You can teleport before or after the additional action.
You would only be able to do this once per short rest, but then, that's as often as an Eladrin can use Fey Step anyway. When you Action Surge, you will be able to teleport 30 feet (which is what Fey Step can do) and you still have you bonus action, plus two actions to then make a total of 7 attacks (since fighters have Extra Attack (2) by that level).
But like I said, at that point, you're playing an Eladrin fighter, not an Eladrin rogue, so this might not be quite what you had in mind, but for what it's worth, it is a way you can achieve the sequence you are going for (and you don't even need to be an Eladrin; in fact, you could save up your Eladrin misty step and use it to get away again after having made 6 attacks).