Thinking of buying a new telescope. What aspects should be considered? I'm new to astronomy and I have a Celestron 50Z but I'm thinking of buying a better telescope. 
I see that there are many options out there but I'm not really sure as to which aspects I should consider that make a good telescope.

Can anyone point me to the right direction? If you ask how much I'm willing to pay, I'd say up to US $300.

Any suggestions not just on telescopes but as I said, things I should be considering which make a good telescope worth buying.
There are many aspects that should be considered, but a few very important ones are:


New or secondhand? With your budget, buying a new telescope will only get you so far. But if you try to look into secondhand products, you might be able to find something more advanced—well-kept telescopes last years. Of course, you must be careful with whom you are buying it from, and make sure to try it before buying as well as asking about the last time the mirror was cleaned, what eyepieces are included, etc.
Dobson or not? There are many upsides to having a Dobson-type telescope: you get a much larger mirror for the same price, it's easy to set up and maintain... However, it does take more room than other telescopes, and you will have to do more maneuvers to aim and track things with it.
On the same vein, does size matter? If you are looking for the most compact and lightweight telescope possible? If yes, that will have an impact on the kind of telescope you should buy: maybe you will want a Maksutov instead of a Newton, maybe you will want a tripod mount because it can fold and takes the least room.
What do you want to see? As StephenG said earlier, it is important to know your expectations as for what you want to observe with your telescope. If you live in an urban environment and/or are unable to go to spots free of light pollution, that severely limits your possibilities to (mainly) planets and the Moon. To that effect, you might be more interested in a telescope with a bit more focal length. If you are indeed able to go to spots free of light pollution, then you probably want to maximize the diameter of your mirror, because if you get a mirror that is 20% larger, you will get 44% more light.


Some other questions that may influence your choice are: is this a long-term investment or are you looking into making an upgrade in the next few years? Do you want to try astrophotography? How much time are you willing to take to set up your telescope before observations? Do you enjoy using a sky atlas to find the exact object you are looking for? Etc.

To give you an example, I was a similar situation a few years ago. I had a budget of $400, and I wanted a telescope for visual observation only. Because I had access to good observation spots and size was not an issue, buying a Dobson was an easy choice. I joined an astronomy club and a member was going to upgrade his own Dobson (https://www.astroshop.eu/gso-dobson-telescope-n-250-1250-dob/p,6680) to a bigger one, so I was able to test it and buy it secondhand knowing exactly what I was getting.

You should also have in mind the fact that a telescope will often require a few accessories (eyepieces, filters,...) that you might need from day one, so do look at what is included with the telescope you buy, as good eyepieces are things you can keep with your next telescopes, and bad accessories can affect the quality of your observations.

Astronomicably,