First off, Congratulations to Broceratops! I was expecting you to be in the top 3, I was really surprised this morning when I got up and saw you had taken the overall position! I can't wait to drop with you again and see it after I die(If I die...).
Anyway, the last 3 days have been crazy! I started at 3:00 est, so I was late to the party, and just wanted to see how well I could do. I also knew I didn't want to pilot a 3L, first because I think they are easy mode with streaks, armor, speed, and and ecm, and second because I dont even own a raven so I would be at a disadvantage trying to level one up. My Spider has everything but the Master Module slot, which is OK because I only have the Advanced Sensor Range Module as of yet. I have also been trying to get really good with the spider the whole time I have played MWO(SDR-5V was the first mech I bought, I started playing just a couple of days after it was released) so this was my chance to see what my ranking was.
Here is the build I used:
Endo Steel, Ferro-Fibrous Armor, Double Heat Sinks
XL255 Engine
1 Medium Laser in the torso
2 Medium Pulse Lasers in the Right Arm
Guardian ECM
7/8 Jump Jets
Advanced Sensor Range Module
210 Armor, the key to it being have 15 on Right/Left Torso and 13 on Right/Left Torso Rear, and have 20 for both the Center Torso, everything else maxed.
Ok, on to Tactics. I had the Most trouble against Raven 3Ls. As a spider pilot, my advice is to not engage unless there is no other option, or try to lead them back to the rest of the group if they are nearby. Even if your team is nearby, it will be nearly impossible for a spider pilot to spend much time engaged with a 3L. If you must engage them, I aimed for their legs, or if I had the shot, at their back. This can allow you to do damage. Keep Jumping, and jump on and over buildings to try and get their streaks to hit that. Cover is your friend.
Other than 3Ls, my advice is to engage, but always keep your terrain in mind. I can keep all 8 enemy players engaged if need be, but I do have to look out for those heavy hitting one shot builds. Remember what Roger Bacon said, scientia est potentia, or Knowledge is Power. Always target enemies and remember to look in the upper right at what weapons an enemy has and where it has been damaged, and keep in mind the general armor values so you know what you might be seeing in terms of number. An orange atlas ct and an orange atlas back torso rear mean very different things. Always stay moving and use terrain to your advantage. If your team has LRMs, they are counting on you to pick the targets, so don't always choose one mech or the other, but change it up, it can be a nice surprise for an enemy in the open

Regarding ECM, as a spider you have to be active with ecm use. Scientia est potentia again. If you are being disrupted, ALWAYS counter, even if for just a second or two. This allows both yourself and the team to get a quick read of a situation, while preserving ECM superiority. A spider can react quickly on the battlefield, and should go where teammates are being disrupted if not otherwise engaged.
If anyone has any questions, please ask

TL;DR I have gotten better as a spider pilot because of the tournament, finishing 8th in the hard fought light category, and am willing to answer questions about tactics and my experience in the tournament.