For manifestation, you don't need any supplies! Repeating things out loud or in your head while you're in the right mindset is all you need. But there are some accessories that aren't necessary, but help.
1. A journal.
It can be any old journal, from the dollar store or a fancy stationary shop, as long as you can write in it, it's no problem. This is needed for writing your manifestations down, like the 55x5 method, or 369 method (what are you manifesting, what is your intention, and what is the outcome) Great for writing down positive affirmations, things you're grateful for, letters to the universe, etc. You can even print out pictures or use stickers (even draw!) a vision board in your journal. I recommend having a single journal for all of this, and not doing your manifesting in random journals you find around the house. Have one that is specifically yours for this specific thing. Decorating it is also great!
2. Crystals
Think of crystals as little balls of energy. You get them, cleanse them, and charge them, and bam! they're filled with your energy (or the energy of the moon, earth, a deity, etc) Crystals are like prisms, they each have their own special sort of power, you put in energy and you get out energy directed or focused at something. Like rose quartz for example. You put in energy, and the energy you get out is regarding love, happiness, and healing. Crystals are powerful tools! and amazing to hold during manifestation or meditation, to have them on your shelf, next to your bed, under your pillow. They don't need to be big, it's about quality, not quantity! They are amazing for manifestation, especially if you can get your hands on some crystals that concern your specific want.
Now crystals are their own thing entirely, and I'm not going to go into full detail. I may write a guide on crystals another time though. (;3. candles / incense
Incense is good for clearing areas of negativity. Burning incense while meditating is great at warding off negativity and inducing positivity. Incense is also traditionally made of herbs, and if you like Herbalism, this is definitely for you. Different herbs also have their own powers and meanings, and have a serious effect on things when burned. Specifically aiding manifestation and meditation.
Candles refer more to color magic (ex: yellow = happy, green = luck and money, red = romance and anger, etc) Buying candles that are a color that aligns with what you want, and burning it during manifestation or meditation is a nice visual focus.