Anyway...
On exercise, you are going to have good days, you're going to have bad days. Do not push too hard on any exercise, especially if you need some part of your body for other purposes. Like working on feet all day. Injury = loss of motivation + extra time needed to recover + loss of "gains".
Exercise takes time and some amount of attention. If you are just starting out, do something whenever you can in short bursts, and get into the habit of doing so every couple or few days (or even just once a week; something is better than nothing). And if you are sitting for most of your day, basically strength or cardio will affect both, but lean towards strength building exercises. Since stabilizer muscles need time to build and you will get yourself used to breathing (breathe in through nose, exhale through mouth ideally).
With strength training, do your best to ensure you're keeping good form. Both for safety from injury and to not cheat yourself of the exercise results.
I always say bodyweight squats to start. You can do these whenever and just do a set of 5, 10, maybe up to 20 within a minute. Targets a lot of useful muscles, and if you're packing a lot of fat like I did, should open up the ability to do more varied cardio without guaranteed injury. Since you build up those leg and knee muscles + support muscles.
For upper body, pushups (keep trying to do them, but hold a high plank if you cant) covers a large range of muscles. If you can, access to a pullup bar and free weights (even light ones) are great for just general upper body fitness. Like with pushups, if you can't do a pullup (and most won't starting out), just hang as long as you can and keep trying. After a month to three months of constant attempts (that's what i remember observing and personal experience), you'll likely be able to do your first.
(Note for those bars that press against a doorframe: they do work in general, but it's very likely to damage the paint on the wall. Easy to fix for the most part, but just be wary of that.)
Be persistent on doing any formal exercising. If you really do not feel like doing exercise on a day, even doing 25% of your usual routine is better than nothing at all. And on off days, doing 50-60% is fine too.
That recommended 150 or even 75 minutes of weekly activity? Yeah that's great, but I got to that point some 3 years after starting again post hard rebound. 2-3 sessions a week lasting 3-5 minutes to start is what I did (and sometimes just 1 session a week). As I got used to it, I both dedicated more time to it and found more time for exercise. Because I started actually wanting to do it around the second year. Heck, it was the second year I actually felt I could do cardio without massive backlash.
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Now the larger part of the equation is food. You are going to spend time, some mental energy, and probably have some additional expenses on this as well, but same concept as with exercise: take it slow, don't need to do things overly perfect, ideally should feel mostly natural as you make changes gradually.
Do not cut too many calories. I personally found 1 pound a week (500 calories deficit per day) too difficult and rebounded hard. I was and still am able to do around 150-250 deficit though (so half a pound a week or less), and maintain + lose more.
(Even at a low calorie deficit, you're likely to "feel a bit hungry". Give your body and brain time to adjust to that feeling.)
Get into the habit of writing down how much food and drinks you take in. To give yourself a realistic idea of how much you take in, and finding where you can replace/substitute/cut back. You don't have to be too accurate starting out, as again, it will take too much time.
Protein is important for building muscle mass and maintaining, but if you are starting from almost nothing, you'll likely have enough protein anyway.
Easiest starter to cutting calories is to drink more water. Highly recommend at least a single stage filter of sorts and non plastic water bottle. Drink some if you're feeling hungry earlier than you like, or if it's late and you don't want to eat. But staying hydrated properly is just good overall beyond hunger.
From there, it's really just slowing down on intake. Maybe replacing "junk snacks" with fruit on occasion. Or just lowering the amount of junk slowly. I was at roughly 2400 calories a day years ago. Took me over a year to cut my intake down to about 80-85%, then another year to cut it to about 70-75%, and now i can maintain 65-70% without issue. The "70%" now makes me feel full, and eating "80%" makes me feel bloated.
If you are mostly eating "junk", take a multivitamin supplement. The ones from say Costco are fine enough. They do nothing short term, but should help your body function properly in the long term.
...Now this is not quite "fitness", but if you can, try learning to cook a couple things for yourself. A lot of restaurants and pre-prepared food are loaded to hell in oils, salt, added sugars, and whatnot. This one is a huge time investment (both the cooking and cleanup it entails), but it would save you money and likely help you achieve fitness goals over time. Contrary to this chapter, a couple pancakes with butter are not going to overload you on calories. Not unless you keep doing it every day.
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Now if you're talking gains, specific exercises, etc, you can look up various things online. Running, lifting, high intensity interval training, yoga, or whatever. A lot of the websites out there seem to cater to people already into fitness. And a lot like to have horrendously unrealistic goals for the average sedantery dude. Nevermind an out of shape and obese sedantery dude. Which I was.
This also applies to food and cooking really.
I don't doubt there are several people that can make drastic changes and maintain it "effortlessly". But that didn't work for me.
I'm not entirely sure what "fitness tips" is to you, but hopefully, there's something here that might help you reach your goal. Or perhaps start it earlier.