Here's a quick screen shot of my food today...
Definitely not enough cals if you are going to add any appreciable muscle.
I'd start with at least 18 calories per pound of body weight and that's probably not enough given your current build.
That said, this is all working under the assumption that you are training properly, which we'll discuss.
Looking at it I don't think it's nearly enough calories but this is a lot for me...
Mind you, you don't have to eat as much as I suggest all at once. Your metabolism is a very adaptive piece of machinery. Start adding food to your meal plan every week or two and your metabolism will adjust to make it more 'comfortable.'
I eat an average amount of food but I make sure it's "healthy" stuff. Here's a typical day:
Breakfast - Fruit smoothie or porridge
Snack - 2 apples / pear etc..
Lunch - Sandwich + fruit piece
Snack - Some ham and fruit or something.
Dinner - Fish + Rice / Pasta etc.. just a "good" meal.
You need more protein. I'd shoot for 1 gram per pound of body weight, assuming you are relatively lean. Add some protein at breakfast. Think eggs, cottage cheese, possibly a whey shake, etc.
Instead of a sandwich at lunch, you'd be better served eating a breast of chicken/turkey or the like. If it's a possibility, then I'd recommend pre-cooking it so you have a 'stash' of it to pick from for a few days before cooking in bulk and refrigerating again.
Overall, I'd change your snacks around a bit... get more nutritious with them. Add in some nuts here and there to get your essential fats in. More veggies. Definitely not enough veggies in the diet. I'm rambling here... but hopefully you catch my drift. I'm not a fan of giving specific nutrition advice over the web. I like to shed some light on the 'mentality' behind a proper diet and have you fill in the gaps with the foods you like.
In general:
Protein: Chicken, turkey, pork tenderloin, fish, lean ground beef and steak, eggs, cottage cheese, whey, etc.
Fats: Nuts, natural peanut butter, fish, fish oil pills, flax, extra virgin olive oil. avocados, etc.
Carbs: Whole wheat pasta/bread/wraps, yams, sweet potatoes, rice, old fashion oats
Fruit is great, but you need a lot more veggies in there. If you have trouble getting enough veggies in, you might want to try a 'veggie supplement.' Something like Greens+ or the like.
At home I do the following exercises roughly 4-5 times a week:
~50 natural press ups
~30 diamond(?) press ups - with one hand on top of the other under my chest
~40 military(?) press ups - hands shoulder width apart
What are natural press ups? Do you mean push ups?
How do you do your military "press ups?"
A whole lot of upper body pressing and no pulling = unbalanced = trouble down the road.
Also, if you go to a gym, why do you do all these calisthenics from home?
And for abs:
15 crunches i think they're called (sit up but not fully up) then hold the last for 15 seconds. I try to do 5 sets of these.
Holding sit up mid-position for 20 seconds, rest for 5, repeat for sets of 10.
Same as above but slightly slanted so I feel it in my sides.
Meh. I wouldn't be wasting my time on this. A handful of weighted crunches a couple of times per week will suffice.
In the gym I do:
Set of 10 heavy weight bench presses
Pull downs x 20
Bicep curl x 15
Pectorals(?) x ~20 - Sat down, arm either side and pulling it together in front of me.
Honestly, I'd ditch the crap you are doing at home and throw this routine that you do in the gym out. You should be training your legs. Why aren't you?
I certainly don't want to simply throw what you are doing out like it was garbage. However, from my perspective, it is far from optimal. If you'd like some suggestions on what I'd do to improve the routine, great. If not, that's fine too.
If you do, how many days per week can you get into the gym? How much time can you allot to training?
Ideally, you can make the gym 3 days per week for 45-60 minutes of resistance training.
And repeat. These are pretty much as many reps as I can do. I'm not sure whether I want to go for low reps of heavy weight, or more reps of lighter weights, or even mix the two?
Depending on what you define as low and high reps, I'd answer this question by suggesting a mixture of the two.
However, I like the base of my routines to be based around low/moderate rep ranges.