Good suggestions above. Start with the practical and just keep shooting as much as you can right now. Lens cleaner -- easy way is to use a little blower to remove dust, then use a Zeiss wet wipe and a microfiber cloth to dry.
UV or clear filters can be used for protection, but a cheap filter will reduce the quality of your images. A good filter can cost almost as much as some inexpensive lenses, so some people only buy the expensive protection filters for their more expensive lenses. A circular polarizer is a good idea for outdoor shots and to reduce reflections (glass, water, etc). If you are going to spend good money on a quality CP filter, it is best to buy a large one and then buy "step-up" rings to fit it to the filter diameter of your smaller lenses. Neutral density filters (solid or gradient) reduce the amount of light that enters your lens, allowing you to use a wider aperture for shallower depth of field or a slower shutter speed. CP and ND filters take practice.
It is hard to suggest a bag when you don't know what type of gear you'll be bringing, but for the camera and 18-55, a Zing wrap works really well until you do. You can throw the combo into a backpack or something until you know where you're going in terms of extra lenses, etc.
A good neck strap is also well worth the money, consider straps (Optech, Tamrac) that have quick releases so you can remove the strap when packing or shooting on the tripod.
A tripod is also good in general (for travelling, that is your call). Get a fluid-head if you want to shoot smooth panning (i.e. videos), or get a ball-head if you are basically looking for stills. In terms of quick-release tripod heads and camera plates, everything is brand specific except for those that refer to "Arca Swiss." AS is a brand but also a type of dovetail that is basically public domain and so lots of manufacturers use it. Also something that you can find lower-cost options on Amazon. Some tripods come with heads, some are just legs and you buy the head separately.
A remote release is a good idea. The wired ones are best, but the wireless remotes can be used for selfies. (I have a Canon brand wireless and a generic wired remote with a built-in intervalometer...)
As for lenses, lots of people here will spend your money very quickly. If you are new to photography, you can do a lot with the modern "kit" lenses (18-55, 55-250, 18-135). Plus they are lightweight and easy to carry around. The best camera is the one you have with you -- and use. There are some inexpensive lenses that are a lot of fun, especially the 50mm 1.8 and the 40mm 2.8. The 50 is a little older and a little bit longer, but it lets in more light and creates a shallower "depth of field," meaning more blurry out-of-focus backgrounds (often called "bokeh"). The 40 is newer, smaller, quieter, focuses a little more closely, and has a slightly wider field of view. The 28mm 1.8 or 35mm 2.0 (not the IS version) can be had used for a little bit more than that, and they make a good "normal" lens with a wide aperture like the nifty 50. It is hard to find an ultra-wide lens for APS-C (or "crop") sensors, but the 10-22 is well liked and can be found somewhat inexpensively used. These can make for nice landscape photos, but you can do those with the 18mm end of your zoom, too. If you are into taking pictures of flowers, bugs, etc, consider a macro lens (50mm 2.5, 60mm 2.8, 100mm 2.8 ). Look at completed listings on eBay to get a good idea of used prices. The third party manufacturers make a lot of lenses, too, but I don't have much experience with that. If you are just starting out, consider a standard zoom (your 18-55), a telephoto zoom (55-250 or 70-300), and a fast "normal" lens (28/35 on crop).
You have a pop-up flash on your Rebel, and that will work for "fill flash." Consider buying a "Gary Fong Puffer" for your pop-up. It is a lightweight and easy way to soften the light and avoid the "deer in the headlights" look. The next step up is something like the 430EXII which has a swivel and lets you bounce the light around a modify it.