Yup. You need a pair of Duluth Tactical pants. Best investment I ever made. Way better than the 5.11's, and a better price. Seriously though, a couple more pairs of jeans are never a bad idea. A few different colored dress shirts, ties, and pocket squares can help to vary the appearance of your suit. You might want to look into getting a vest; you can wear it with your suit, or without to dress up just about any outfit.
It depends on what you do now and want to do in the future. I really can't answer without knowing that. There were some good articles on the main site a while ago about building a wardrobe, with examples for various types of work and lifestyle.
Depends on what your goals are. I have plenty of work jeans, shirts and tactical pants. I recently upgraded my wardrobe with some nice clothes to wear when I leave the house with my wife or children. Five plaid slim fit dress shirts, two nice dark blue jeans, two V neck sweaters in neutral colors, two pairs of dockers slacks, and a charcoal sport coat. I wear work jeans and t shirts around the garage or when i'm cruising on my bike. Now I don't feel like a dirtbag going out in grease stained jeans that smell like gas when I'm with the family. I think it is important to teach your children how to dress respectfully.
A big +1 to Nathanael's reply. Unless you give some information about what yourself, i.e., your age, what you do, or intend to do, a list of your current clothing is pretty useless...unless of course, you're a member of Black Block or a die hard Occupy afficiando.
My essential wardrobe is very different from yours. When I read Tactical pants I had a vision of canvas pants with tactical webbing all down the legs for adding bags like the tactical vests and backpacks. I suspect you mean a good sturdy set of pants.
For me I have a focused business dress wardrobe. The goal is to maximize the number of outfits and minimize the number of items. I have found that I need to put a few pairs of pants and perhaps a shirt or two into seasonal storage so that I can keep wardrobe smaller but add variety without having to buy something. I think you get a point where if you really enjoy dressing well things start to feel stale. Rotation helps that.
I also have clothing for after work when I cook / lounge about the house, general construction work/ muddy work, gardening, and hunting.
The question is when you say improvement what are you thinking? I could suggest an entirely different style then you are and that would not be helpful.
It sounds like most of your time is spent in pretty casual ways, as far as clothing is concerned. You're taking care of a kid (or kids) at home, and many of your hobbies can get messy. Most of your clothing is geared toward that, and should remain so. You've got a suit (and presumably at least a dress shirt and tie to go with it) for more dressy events. I do see a couple possible ways to improve your wardrobe, however.
1. Better casual wear. You could consider wearing more polos or short-sleeve button-down shirts, for instance. Wearing one of those over an undershirt (to soak up sweat) with khakis, jeans, or 5.11 pants (I used to wear those a lot) is a good, casual look for a lot of men. Cotton sweaters can be good too, in colder weather. It's not a huge shift, but it makes some difference. I did something like that when I went from undergrad to the workforce.
2. Something to fill the gap between casual wear and a suit. Basically, a sport coat, some nicer khakis, and a long-sleeve button-down shirt or two.
I guess it's all subjective because I'm not sure I really know what tactical pants are but I'm pretty sure they're not essential to my wardrobe! ;)
"Tactical" is a catch word. Tactical pants generally are cargo pants that are made out of tougher materials and have hidden magazine pockets for those who are in military/law enforcement trades. People who carry concealed benefit greatly from them as well.
If they are what I'm envisioning (and wearing, at the moment) they're basically navy cargo pants with extra loops for holding shears and such. I know them as "EMS pants", but I've heard them called tacticals or "Tacs" before.
Nothing wrong with cargos or tac pants, but a guy definitely needs more than that in his wardrobe for smart/casual wear.
You should have some dark jeans and khaki's or chinos (all flat front) for when you are going out, a few casual oxford shirts and sweaters (v-neck & crew neck) and some leather boots and shoes (plain gibsons or casual brogues) as well.
A few lightweight jackets...Harringtons, Blousons, that sort of thing.
I also 2nd the suggestion of a sports coat or 2, they are very good for smartening up a basic pair of jeans/trousers and shirt for a night out with the wife or whatever. Make your first one a dark grey/charcoal colour, very versatile IMO. And as somebody who is "well built" nothing is going to flatter you/taper your frame like a nice sports jacket/casual blazer.
Oh, and some white tees for under those shirts...no black!
That's your basic "casual wardrobe essentials" as for dressier stuff, that's pretty basic, some smart dress shirts, a handful of ties, some dress pants (flat front again), some nice dress shoes and a suit or two.