I'm going to save you some money in the long run.
Don't buy a cheap set of legs.
Don't buy a cheap filter.
Just don't. You will end up re-buying something later. And then again. And ultimately spend more than you originally would have had you just gotten a good set early on. I wish I had listened to this very advice that was given to me here. I didn't. And I went through several sets of legs and filters. I wasted time & money. I should have listened and got a good set of legs and ballhead and good filters the first time. But, we all live and learn in our own silly way. So, if nothing else, I will pass on this lesson that I had to learn the hard way. Wait. Save up. Get something good.
There's actually a ton of good legs out there and good ballheads. And there are end-game setups too. But I would not limit this to $100. I would expand that. To get the ball rolling, maybe look at the MeFOTO Road Trip (Aluminum). Not expensive. Quite good for what it is. Otherwise you can mix things, like a good set of Benro or Induro legs (same thing, great quality, good price) and a separate ballhead, like a Sirui k20x. End game setup.
As for filters, it really just depends on what you want to do. Filters really are not necessary anymore in the digital age. The only real filters to consider would be a good quality CPL (polarized) like a Marumi or B&W CPL, and maybe ND filters of various strengths for the purpose of long exposure duration in day light. That's it. And if you go that route, you don't need a full set of ND filters, really just need one or two and that's it. Like a 3 stop filter and a 10 stop filter, or a 6 stop filter and a 10 stop filter. Again, B&W, Hoya, etc, make great filters. I will however throw a recommendation for BreakThrough Photography too here, they are costly, but pretty much zero color cast, quite nice filters. Again, these are not cheap. None of these are. But you will regret a cheap filter. Don't waste your money on cheap filters. You will regret it. I would recommend a single 6 stop filter as a good starting point. Or, just go ahead and get a 10 stop (B&W or Hoya or Breakthrough Photography) if long exposure is where you want to go.