If wanting to save money, there are tons of great synthetic polyester baselayers that are cheaper than merino wool and also wick away sweat will to prevent that cold/clammy feeling while snowboarding. The downside of synthetics is that they retain more odor if you are on longer trips without a washing machine (usually after 2-3 days), but they are more durable and easier to wash like @Doraibu said. Perfectly good alternative to merino wool depending on what you need. I have a 6 year old Hot Chili synthetic baselayer that still works great. Definitely very durable.Top notch thanks again for this money4me247.
For the wax to maintain the board, do you have any kit recommendation?
And also: as a beginner, should I mount the bindings on my own or leave a professional doing so?
For waxing, you really just need a iron, plastic scrapper, and wax. Kits usually have more than you need, but if you want to get more into other snowboard maintenance, it can be helpful. Demon and RaceWax both have a wide variety of good kits at different price points depending on what you are looking for. For a snowboard iron, nicer ones have digital display or digital temperature control or a larger base to retain more heat - but really any iron will work (some people even use clothing iron - but can't iron clothes with it after it gets wax on it). For plastic scrapper, a larger one is better since you can scrape off more wax with each pass. For wax, I just buy a large block of all temperature wax because I go snowboarding very often (there are tons of wax companies: Demon and Purl have well-priced 1lb blocks). For more performance wax, Hertel is a very popular and frequently recommended brand. There are also temperature-specific waxes that perform better at their listed temperatures. There are tons of wax brands and options but I would avoid rub-on (without iron) wax as it does not last very long. There are fancier things like brushing your board (brass brush before to clean the base and some people use 3 brush pass afterwards with brass brush, nylon brush, and horsehair brush) but usually only important if racing. Note there are many people that don't bother waxing or just take to the shop to wax.
For bindings, I would definitely recommend that you learn how to put on your own bindings (and how to change stance angles and change stance width). It is extremely easy once you learn, just need a screwdriver, and your bindings will come with a manual.
Bindings will have a separate piece that is a circular base plate that you rotate for your stance angles and screw into the inserts on the snowboard at your desired stance width. Stance width is usually slightly more than shoulder width apart - usually the properly sized snowboard's reference stance markers are very close. Make sure you tighten the screws very well so your bindings don't loosen while ridding. If tightened by hand as hard as you can usually stays in place very well, but should check before every trip that your bindings aren't loosening. If it happens on the mountain, all resorts have areas with screwdrivers for tune-ups and many snowboarders carry pocket screwdrivers and the on-mountain shops/rental stores can help as well.
I also carry the Burton EST tool so I can tighten my bindings or adjust angles/stance if needed. Being able to set the tool in a right angle really helps being able to crank down your screws.
Also, you want the midline of your foot/boot at the mid-line of the snowboard (ideally minimum overhang at the toe/heels, if any overhang should be symmetrical amounts). If your snowboard boots are size 11 or larger, often will need a wide snowboard depending on your stance angles to prevent overhang.
You can post of picture after your bindings are attached on your board on the forums if you have any concerns and people will help you out.