Pick any international party (just google international party, tokyo) and go there. They are usually cheap, like 3000yen for all you can eat and drink.
You have said you are 6foot tall, ‘solid looking’ and work out, as well as having youth on your side. This will put you in the top 5% of guys at any international party. The girls will come to you, you wont need to approach them.
You’ve also mentioned you are inexperienced and slightly socially awkward? Doesnt matter at an international party. Most people there are the same (at least the socially awkward part). The fact you speak english will be interesting enough for the majority of ladies there who will get a kick out of practising their English with you. Be prepared to answer the following questions at least 50 times;
Where are you from?
Why did you come to Japan?
Can you eat sushi?
You’ll be fine and will find people to hang out with easily.
As for p4p stuff, with your budget Id avoid it, as you are not experienced and dont speak japanese your options will be very limited and you are more likely to come away dissaapointed than satisfied.