The best environment for rituals and spell work depends on you as an individual and the things that may enhance your ritual experience. However, having said that, there are several factors important to consider in choosing your ritual space.
Silence/No interruptions is especially important for any ritual space this means you need quiet and privacy to perform your rituals. You cannot focus your intent and energy in a distracting environment. I recommend something with low to no lighting in an area that is relatively soundproof.
Turn off devices. Devices are major distractions and major energy drains. This means the TV, the radio, your phone, your PC etc. This will help with mental silence as when you are constantly reading a screen your brain operates at a different frequency. To raise your frequency, you need to avoid having devices in your ritual area. With covens I have been involved with we had a practise of putting all communication devices in a basket until after the ritual was complete. Focus is really important; distraction can be the cause of spell work fizzling out.
Outdoors vs indoors is another consideration that comes into play with ritual settings. Ideally, we all should practise outdoors to utilise the power and frequencies of those elements of nature around us to full potential, it also helps with balancing and keeping energy grounded as well. However, this is not always possible. So many of us are forced to practice indoors. Its sometimes not even possible to have a spare room for the purpose of ritual so in light of that, of all the rooms that could be considered quiet and private and free of distraction, it would be the bedroom. The room you choose will depend on what kind of space you are working with, your lighting requirements and your ability to obscure things like altars. I have a dear brother who uses his shoe closet. This is a perfect choice re privacy, minimisation of distracting influences and space with lighting requirements. Plus, he is able to obscure his altar from prying eyes.
Astral Temples. Astral temples are used in situations where you do not want others to know what you are doing, or if you live in a small space, shared with a family or many people. I have had many friends living with a Christian family, unable to have a ritual space or be free to practice, so I have helped them with this meditative technique. Upon achieving the necessary psychological and metaphysical state of projecting yourself, (practice of meditation is recommended to ensure one recognises this state confidently,) you may freely choose a psychologically derived landscape that feels private, clean and feels right for you, such as a forest, etc.
I will show you how to make a temple to Asmodeus for example. To make an astral temple you need to meditate for a while. You visualise yourself following a path down to a stream where you find a large tree with a trunk the size of a large house. There is a hole in the tree trunk that you can crawl through. You visualise crawling through the hole until you find you can stand. There is the dim light of candles glowing against lavishly decorated walls. You visualise walking into a large cave with a central pillar and an altar. The air is ripe with the smell of smoke and the crackle of fire draws you near to a large camp-fire in the southern centre of the room. You continue with this imagery and you begin to lay out your ritual tools on the stone altar in the northern centre of the room. You pick up an already burning sage stick and the air is instantly filled with the aroma of cleansing and purifying smoke. You begin to chant the enn of Asmodeus. You scry in the bowl of cold pigs blood the sign that tells you HE is there. You may then petition Asmodeus. You sign the petition with your own blood and burn it in a fireproof bowl. You bid Asmodeus farewell and thank him for coming. You cleanse your space and crawl back out of the tree, locking the entrance with a magickal charm.
By doing the aforementioned exercise each time you wish to do a ritual (the details of which you will plan and write as an addendum to the exercise for use in the Astral Temple) you go into your Astral Temple in exactly the same manner each and every time.
Cleanse your environment no matter what this is the most important step in making your spell work and ritual environments safe and clean. Cleanse, cleanse, cleanse. Sage the room and all of your tools before and after rituals. Sprinkle salt water on window ledges and around doorways, hang charms in the corners of room to ward off troublesome influences.
If you are on top of these things your ritual experience should flow more smoothly, and it will help raise your energy and vibrations in your ritual/spell work.