Entertaining rule #1 is to not experiment on guests!
Since you're a novice my advice is to not complicate things by thinking of marinades. Just focus on cooking your steaks properly. Rare, medium rare, medium, medium well, etc. I'm sure somebody will post advice below on how to tell the difference. I hate the thought of trying to cook several orders ranging from rare to well. I'd rather just kill everybody who doesn't like their steak medium-rare.
Yes the rule is to not cut the steaks while cooking, but my advice is pick one that will be yours and when you're nearing the time you think they're done cut a piece off your steak and taste it.
And when your steaks are done cooking, let them rest for at least 5 minutes, maybe 10 minutes, before serving. This has to do with the juices. Maybe somebody (below) will explain it.
Serve with a few selections of steak sauces, perhaps A-1, Lea & Perrins, and maybe some horseradish (if I'm invited).
See if your market or deli has stuffed baked potatoes (often cheese, sour cream, etc). If so, get their advice on how to cook them. Otherwise, steaks are traditionally served with baked potatoes, sour cream and chives (or green onions).
A salad with that would be good.