Personally, i start every single fortress with 2x fighter dwarves and immediately put them on training when i embark (just put them in the corridor on the entrance.
All they need to begin with is weapons. Getting them shields early helps also (wood is probably the best, try and get good quality ones).
With 2x copper swords or 2x copper warhammers or 2x copper axes and given maximum training time they will slaughter all early goblin rushes (presuming goblins have no/minimal ranged attacks).
If you use therapist, you can see easily at embark, which are you two best dwarves for the role (speed/strength is what i look for mostly, but the other stats matter also), without it, you can just have a good guess anyway. How good they are with weapons matters little, as it will change if you've put 5 points into their weapon ability.
I put 5x points into weapon ability and give one of them 5 points in dodging. Occasionally i will give the other 5 points in armor/shield use, as this helps them learn these abilities one heck of a lot faster. (i.e if you didn't get either of them dodging, it will take ~3 years to get a noticable level of it, whilst if you give one proficient, this will improve +1 per year and the other one will match it in a year)
I will then personally equip them in copper if i can get any (or embarked with ~20 copper ore), if not, i purchase iron and sell roasts (i bring a cook with me also) and use that for new weapons and armor.
This is just a personal way of doing things, i believe using leather is equally effective for armor.
You may say this is very costly, using 2 of your first 7 for your military, but on the other hand, i've used this squad of two, to take out 30+++ goblins and receive no damage in return. It will also possibly save you dwarves, if defending yourself has been an issue.
If you do not wish to use 2 of the starting 7, i suggest using 2 of the next wave, choosing the ones best in weapons (again therapist) and start then. Make sure you can make 2 weapons (i personally don't like training weapons, i very rarely get injuries from training, it only seems to happen when you have a skilled dwarf versus an unskilled dwarf).
Lastly, train them in squads of two, to encourage sparring.
4x squads of two will completely annihilate one squad of 10. Make sure these squads of two use the same weapons, not necessary, but again helps as they train each other in those weapons and learn them faster than mixed (based on own playing, not 100% sure how accurate this is, i do know mixed does work also, but never seems to be as good)
Given that, here's how i defend my fort at x years with ONLY melee and no other defense (although traps are also excellent)
1 year: 2 dwarves
2 years: 2 dwarves
3 years: 2-4 dwarves
4 years: 4-8 dwarves (may get one injured in fighting at this stage, replace should this happen)
5 years: 8-12 dwarves
6 years+: generally should be thinking of other ways of defending yourself. melee can only do so much.
even with ~10-20 melee dwarves, fully equipped in decent iron equipment, you should still reach ~10 years against armies of 80 goblins. My forts usually collapse because they're unhappy their military friends have died in combat and can't seem to get over the spiral.
I would suggest if the cost is an issue of getting 2x proficient weapon users, one with proficient dodging to use copper short swords. (if cost is really an issue, bring copper and forge your own swords). Whilst these are pretty poor later on, they are good enough for 3 years until you can trade for better weapons.