Lets start with saddles.
They are NOT all created equal. All bikes come with a saddle (this sounds really obvious now that i've said it) but it doesn't necessarily come with the RIGHT saddle for you. I did not know this for the first 4 months of my riding experience.
I call this an experience because I just didn't know all the thing's that I didn't know. It's the unconcious concious (I'll let Wiki explain it here) but basically it's the things that you might need to know but don't know yet. I simply did not know that the seat on my bike was making me VERY uncomfortable.
I wriggled a lot. I didn't say anything to the people I was riding with and then one day I did.
Knicks are a separate conversation but let's just say that the saddle conversation was life changing (*slight exaggeration - the life changing bit was actually buying a bike in the first place!) but it really was a moment in time that made me stop wanting to throw my bike at someone and instead it made me actually enjoy getting on it.
There's LOTS of websites about saddles and the "right" one. The one that is right for you isn't necessarily right for me. If you're on a commuter bike then you don't need a racing saddle. If you're riding a short distance then the saddle you use may not be as important as if you're riding long distances and multiple days in a row.
There are a huge range of saddles. They are not all stocked in one place which makes it VERY confusing but in short - there will be a saddle that feels right for you. I'm up to my 4th saddle. That's in 3 1/2 years. The first one which came with my bike didn't last long (too long but not long). The second and third were the same type of saddle - a Selle Italia something. I wore through the sides of them within 12 months. That's an expensive exercise right there! Then I found a Bontrager saddle that has been AMAZING and its nearly 18 months later and I still love it.
Many shop's / brands will let you change over your saddle if it isn't working for you within a certain amount of time. I think it's sometimes worth doing this - you might end up back where you started but you don't know what you don't know even though its a bit of a pain in the butt (*pun intended)
Do you need ANOTHER pair of shoes? The answer for me is always. Except in Cycling. I have 2 pairs of shoes but I know many who have more! A lot more! Some shoes are for climbing, some shoes are for commuting, some for mountain biking, winter shoes, summer shoes.
My point on shoes is... Buy the most expensive pair you can afford at the start because they will last you a very long time and a good pair of shoes will save your feet, your knees and your legs!
There are good knicks and then there are bad knicks.
I have to take you on a bit of a journey back to when I was buying my bike. I'd just spent what I considered to be a decent amount of money on something that I didn't know if I would love or hate. I'd bought an average helmet, I'd bought a bargain of a bike, I'd bought pedals, a lock (a useless one, will cover locks later) and I bought knicks. All of this from a guy. I had LITERALLY no idea about bikes. Nothing. I went shopping on my own, I made decisions on my own and maybe in hindsight if i'd asked a few more questions things would have been slightly different but this isn't what happened.
I did get sold the right size bike (very very important!) and the necessities. When it came to knicks though, the conversation went like this "well if you dont enjoy riding then you won't have spent a lot on knicks". Hmmm. Here's the problem. Bad knicks are VERY bad. Possibly the most uncomfortable product i've ever bought.
Like saddles, what works for me won't necessarily work for you but this is where I think I got lucky. If i'd started riding 10 years ago - I'd probably be wearing men's knicks with the seams in all the wrong places. Fortunately, my late arrival into this sport has meant there's a world of women who have gone before me and forged the way for some exceptional knicks that are for women. The industry is still incredibly male orientated and that's fine however I can guarantee that if a guy had to wear knicks with a seam in a very uncomfortable position for a long period of time, he would most definitely want a change.
Lucky for me then that even in the last three years there's been some incredible brands putting out beautiful products for women specifically and for that I think we are all grateful!
Like everything in cycling this is all personal choice and what works for me won't necessarily work for you but here's some of my favorites in the clothing department.
Gloves, arm warmers, leg warmers, caps (not hats), head warmers, shoe covers, base layers. Holy moly. All the stuff!! Do we need this much stuff??
A little bit yes and a little bit no. Somehow, I've ended up with many many many pairs of arm warmers. They were all I could justify spending money on in the beginning. $20 here, $20 there seemed better than spending upwards of $100 on a jacket. Silly me. A jacket is a MUCH better investment.
Buying a good jacket will keep you warm in Winter. Buying a good gillet will keep your chest warm in cooler weather or at the start of a ride before you've warmed up.
Everyone runs at a different temperature so while someone will over heat with 2 layers, someone else might overheat at 3. The outdoor temperature with wind chill taken into consideration is a huge influence on what to wear.