This is a simple strategy that a terran of any level can use to move up to platinum or even diamond if executed correctly.
Three Rax Build
10 supply depot
13 refinery (3 in gas when done)
15 upgrade Orbital Command
This is the standard terran opener used in nearly every strategy, master it.
Once you upgrade your OC, build a marine at barracks_1. Use it to kill off their initial scouting worker if they have one. (If they steal a gas, don't worry, you only need the one).
Build another supply depot, don't forget to mule. When that first marine is finished, build a tech lab addon and start making marauders from barracks_1. After that depot, you should have enough for a 2nd barracks.
At some point here you will have 100 spare gas where you can start researching stim.
Keep building scv's (should never stop).
Once barracks_2 finishes, immediately make a reactor on it and start barracks_3.
Continue making scv's, marauders, muling, and adding depots as needed.
Once barracks_3 is finished, build a tech lab on it and start making marauders there. The tech lab on barracks_3 should start concussive shells.
If done correctly, you should have constant production scv's, as well as constant marauder production from barracks 1 and 3, as well as constant marine(x2) production from barracks_2.
Push out at around 55 food (stim and concussive should be done easily by then). While pushing your opponent, build a Command Center at your natural expansion.
You will likely win. If not, you will be roughly even in terms of army size (if you didn't forget to keep building units while you pushed). You will also have a second base from which to gather.
Once your natural is up, build 3 more barracks (2x tech lab, 1x reactor), and push at ~100 food.
This is not an unbeatable strategy, but it will get you into diamond if practiced and executed correctly.
More strategies to come :)