Appreciate the info that helps us to better understand where your at as far as body and fitness level, and thanks to being open for suggestions cuz that helps you the most Now for a couple suggestions:
First of all let me say congratulations on the weight loss and better lifestyle changes! Isee you were 233 before and now your around the 170's that's awesome brother. Plus also I see your eating turkey, chicken, and veggies and that's a huge change for a better you, kudos to that brotha.
Second my next suggestion for a better diet and lifestyle would be to figure out what your TDEE (Total Daily Energy Expenditure) is you can ask the almighty google and she point you towards a ton of the calculators on line. Then I would suggest you get an app for your phone to track your total calorie intake. I would suggest MyFitnessPal, or MyPlate as both of them are free, easy to use, and even have scanners to read barcodes on what you eat and it plugs in all the info. They can also set macros for Protein/Carb/Fat intake for the day, I love mine! I see your eating healthy which is commendable, but the more you dial in the diet the better results you will get from gear. Also depending on whether your trying to lose weight or gain muscle will depend on what your calorie intake should be above or below your TDEE.
Third there is nothing wrong with starting off with 300mg of Test, you will still see plenty of results from that don't let ANYONE tell you otherwise! As far as adding anymore gear just go with test, learn the ropes and how your body reacts. You can add another compound your next cycle if you do some research and feel your ready or better yet just run 500mg of test for your next cycle if you like the results you got.
Fourth as far as your AI (Aromatize Inhibitor) which is Aromasin is concerned here is where it gets tricky. The problem is everybody reacts to gear differently. So some people can take 500mg of test and need very little, others are e2 (estrogen) sensitive and cant take test without an AI on hand. But the thing you should know is that there is a difference between Aromasin (type 1) and Arimidex (type 2) which are the main 2 AI that everyone uses. Some info here:
https://musclegurus.to/forum/general/general-chat/112884-worth-a-read
now what that means is that the arimidex will lower estrogen while aromasin is much stronger and can crush it. Now considering your body MUST have estrogen to operate, the key now is keeping your e2 not to high or low but in the sweet spot. Now that goes back to whether your e2 sensitive which you wont know until you take test, and also it comes into effect in how much gear your taking as to whether you need arimidex or aromasin and how much of a dosage. Example 300mg of testosterone by itself wont produce anywhere near as much estrogen as Dbol, Deca, and 500mg of test combined. So therefore someone taking 300mg of test arimidex should work just fine, compared to someone who is running a whole bunch of gear with high e2 conversion like dbol and deca will need either stronger or more frequent doeses of arimidex or aromasin which is much stronger to keep their e2 under control. So for you my first suggestion would be to take arimidex instead of aromasin if possible. Also be careful as Aromasin is a much stronger AI and 12.5mg twice a week can crash your e2 if your not careful, so I don't think I would dose more than 6.25mg twice a week and see how it goes. Even that may be too much depending on how you do with e2. This is why we always recommend test only for first cycle!
Fifth your going to want to research and see what the symptoms of low and high estrogen are. Make yourself familiar with them and look out for them as your going through your cycle. For me when my e2 is high my first sign is acne flares up among a couple other things but that's my personal experience and everyone is different. When my e2 is low my joints will ache among other things and its a bitch. So do some research, and blood work half way through your cycle will let you know exactly where you stand! so do it! Bloodwork info here:
https://musclegurus.to/forum/anabolic-steroids/new-to-steroids-start-here/101634-the-basics-of-ordering-bloodwork