Battletech came *WAY* before Mechwarrior did. Mechwarrior is the FPS version of Battletech.
My suggestion? Start out with 'tier 1 tech', or '3025 tech' as us old sweats call it. No Clan, no Madcat, no Double Heat Sinks, no "I WIN" buttons. Play with some of the old mechs first, get a feel for the mechanics. Then move your way up the timeline. Play out the first battle against the Clans, and you'll realize a lot of the hate the really old schoolers have against it. Then progress into T2, which is 'tournament tech'. Clan is mechanically more powerful, but IS generally has lower BV. Still, there's ways IS can beat Clan in T2, if you are smart.
Some things to realize about T1 tech:
1) You aren't going to get a one hit kill. You just don't have the damage output. Most of the one-hit kill builds in T2 involve massing weapons and running yourself into shutdown mode. But you won't have access to any of that stuff yet. So remember, it's not the first hit that counts, it's the last hit.
2) If your opponent is dumb enough to melee with you, be smart enough to kick him in the shins. Take out a leg, and you take out his maneuverability. And kicks do twice the damage punches do.
3) Focus Fire is a perfectly valid tactic. You've got several mechs, and he's got several mechs. Pick one, and completely own it. Move to the next one. The longer they have functioning mechs, the more danger you are in.
4) Battles are won and lost by weapon mix. Energy does not auto-win in T1. There are no DHS to keep you cool while you alpha with 3xCERPPC's. Having said that, don't bother with AC2 or AC5. They simply don't do enough damage to be worth the price of admission. AC/10 is a very viable toy, which generates little heat. Heavy, but fun. AC/20 does insane damage, but has a shorter range, generates heat, and has very limited ammo supply. You can't 'spray and pray' with an AC/20.
5) Use your terrain to your advantage. Getting a pounding? Duck into some woods and loose LoS. Jump behind a level 2 hill. Overheating? Jump into a level 1 water and cool off.
6) SRM's are fun toys for mid-range combat. SRM/6 has adequate ammo supply, and can dish out more damage than an AC/10 if you are lucky, at a much smaller tonnage and crit space.
7) LRM's are fun, but they have their limitations. Expect at least half your volley to miss. They can be devastating, yes, but they don't auto-hit like they do in Mechwarrior.
8) Medium Lasers are the most viable energy weapon in terms of space, heat, damage, and range. They are not, however, godlike.
9) PPC's are not godlike. They do 10 damage, eat up 10 heat, and have decent range. Considering you start out being able to mitigate 10 heat without any additional heat sinks, this eats up a considerable portion of your heat budget. Consider Large Lasers as a viable alternative. They may not be able to headshot, quite, they only take up 2 tons and 3 crits, and still do a respectable 8 damage.
Oh, a clarification on what a 'headshot' is: The head slot can carry up to 6 armor with 3 internal structure. That's 9 points. You need to do at least this much to the head to completely disable it. Whenever you attack someone, rolling a natural 2 on 2d6 on the hit location table nets a headshot. So naturally, you're wanting weapons with more than 10 damage, in case you roll that lucky snake-eye. However, there's not many that can do it. AC10 or AC20 can do it, the PPC can do it... that's about it in T1. Missiles spread out their damage in 2 point increments for SRM's and 5 point increments for LRM's. That's one of the strengths, and weaknesses, of the LRM, by the way. Two clusters of 5 hits the head, and they're screwed. However, because it spreads damage out, you can't penetrate a single armor slot very well. It's good for sandblasting, though, letting other weapon systems punch holes, or for exploiting holes already made in armor.
Charging is not always a good idea. Sometimes, you want to stay at range. For example, closing with a Hunchback, which packs an impressive AC/20, to under 6 hexes, is probably a good way to get slaughtered. So hang back at around 8-9 hexes with an AC/20 or Large Laser or PPC. Pepper him with a few LRM's. And don't let him charge you.
However, on occasion, it is a good tactic. For example, if you are in said Hunchback, your job is to close quickly with your opponents so you can blow them up.
Every unit, even the Awesome and the Atlas, has a counter. Sometimes you just have to be a bit devious.
Damage output is not everything. Take, for example, the sub-par mech the Rifleman. On first blush, he's pretty flippin' nasty. Pair of AC's and pair of Large Lasers. Good damage output at a good range, right? Well, he doesn't have the heat sinks to support a constant drain of 16 heat/round, so if he spams his lasers, he's gonna shut down. And his AC's do as much damage as a Medium Laser, albeit at three times the range. But he's only got one ton of ammo to split between them, which means 10 shots each. So he can't afford to spam with them either, or run out of ammo.
Avoid machine guns. Ammo explosion risk is not worth the piddling damage they provide. If you need something 1/2 ton? Go with a small laser