Which steroid should be avoided for the very first cycle? And Why?

Trenbolone is hands down the best steroid for cutting if you can handle the side effects of course as it has an exceptionally high ratio of anabolic to androgenic effects. Of course, taking it solely is far from ideal for optimal results. I would suggest stacking it with Clenbuterol and Testosterone. For the cutting cycle, Trenbolone acetate is considered the best form of Tren.

Dosage

The dosage consists of a steady 200mg-400mg of Tren per week, usually for 12 weeks (depending on how long you want to run your cycle). Also, the dose of tren is determined by other compounds that you are planning to stack and how powerful they are.
For instance, a quality cycle for cutting with Tren acetate is to take 75 to 100mg two to three times a week for 4 weeks increasing the dosage to 100mg to 150mg for the next 8 weeks of your cycle. Tren acetate is infamous for leaving the body quickly, therefore more frequent injections are required. Using Testosterone with Tren will help keep some side effects in check.