You can't take both Dash and Ready actions
Normally you don't "prepare a reaction". You take the Ready action instead. See Player's Handbook, page 193, "Actions in Combat"
Sometimes you want to get the jump on a foe or wait for
a particular circumstance before you act. To do so, you
can take the Ready action on your turn so that you can
act later in the round using your reaction.
Then you use you reaction (if still available) to actually perform the readied action when trigger occurs. You spend both your Action and your Reaction in this case. Therefore, you can't use your action to Dash after you declared a readied action, because it is already spent.
Unless you have an extra Action, or you're a Rogue
As notices by @NeilSlater, a Rogue has his Cunning Action feature, which allows him to use a bonus action for Dash. You can take the Ready action afterwards. However, this doesn't give you more movement than usual, since you just can Dash twice.
Also, you can't use "my turn ends" trigger
PH requires "perceivable circumstance" for a trigger:
First, you decide what perceivable circumstance will trigger your reaction.
Turns are game mechanics, they don't exist in the game world, hence, are not perceivable by the character, see Can you ready an action for "immediately before my next turn"?
You can move up to your speed using the Ready action
However, the question remains — what if you spent all your movement, and then take the Ready action to move 30ft more? Yes you can do this, providing your speed is 30 (or more) feet:
you choose the action you will take in response to that trigger, or you choose to move up to your speed in response to it
Ready action works like a "delayed Dash" in this case.
The Dodge and Disengage actions are primarily considered as an option to take as your primary Action (PHB p.192):
Dodge
When you take the Dodge action, you focus entirely on avoiding attacks. Until the start of your next turn, any attack roll made against you has disadvantage if you can see the attacker, and you make Dexterity saving throws with advantage.
Disengage
If you take the Disengage action, your movement doesn't provoke opportunity attacks for the rest of the turn.
There are some classes however, that allow you to "Dodge", but these class features aren't the same as the Dodge action. For example, the Rogue's Uncanny Dodge feature halves damage, as a reaction (PHB p.96):
Starting at 5th level, when an attacker that you can see hits you with an attack, you can use your reaction to halve the attack's damage against you.
The Monk does gain a feature to allow them to Dodge as a bonus action, at the cost of a Ki Point (PHB p.78):
Patient Defense
You can spend 1 ki point to take the Dodge action as a bonus action on your turn
And then a feature similar to the Rogue's Uncanny Dodge (PHB p.78):
Starting at 3rd level, you can use your reaction to deflect or catch the missile when you are hit by a ranged weapon attack.
Outside of this, there is very little that allows a player to make these actions as a reaction, or a bonus action.
The only other suggestion I might make is that Matt Mercer's Critical Role series allowed players to use their Bonus Action as "another Action", to basically make things more cinematic. This was generally a spur of the moment decision to keep things moving, rather than to stop the game and check the rules, however.
Best Answer
Reactions are actions that you take out of turn (or possibly on your turn) that happen in response to something else. A reaction can never occur without a trigger.
A Ready action is a special type of action that uses your action to prepare for a triggering event, and when that event occurs you use your reaction to perform whatever you had readied.
To step back a moment, you have four "action types" you can make:
On each round, you get one of each of these things. On your turn, you can use an action, a bonus action (if some class feature, feat, spell, or some other thing grants you one), and you can move up to your movement speed (if you use the Dash action you also move as your action). You also get a free "interact with an object" (does not include magic item activation/use). Whenever a triggering event for a reaction occurs, you can also use your reaction. Anything that requires a reaction will tell you what the triggering event is, except in the case of a Ready action, where you actually determine the triggering event yourself.
A Ready action uses an action on your turn to, as I mentioned previously, prepare for some triggered event which then uses your reaction to perform. So when you Ready you might say, "I Ready my firebolt cantrip to cast at the first orc that steps through that doorway."
This uses your action for that turn. Then, when the triggering event occurs, you can do as you have described, using your reaction to complete the Ready action, OR you have the option to move up to your movement you instead (irrespective of if you moved or not on your turn).
So, in essence, a Ready action uses both the action and reaction granted for that combat round, and once your Ready action has triggered you cannot act again until your next turn.
One other note for readying spells -- when you Ready a spell you actually cast the spell using your regular turn action, and "hold" it until the triggering event occurs. Note that this usage requires concentration. You can cast the spell as long as you continue concentrating on holding it.
It is important to note also that because you only get one reaction per combat round that if you have taken an Opportunity Attack or cast a spell with a casting time of reaction (such as Shield) then you cannot use your reaction to complete your ready action (but you might still have movement remaining). On the other hand, if you have taken the Ready action and your trigger has occurred and thus you've used your reaction for that round, then you cannot cast a reaction spell or take any Opportunity Attacks (barring any special abilities/feats that might grant additional OA's).
Your rogue can absolutely attack (action), disengage/dash/etc. (bonus action from Rogue Cunning Action) and Uncanny Dodge (reaction) on a single turn, but he can only Uncanny Dodge in reaction to a triggering event (outlined in the rules for Uncanny Dodge).