Pre-loading is a good idea. I'm pre-loading myself at the moment for .... a psy-trance night at the weekend
My pre-load is as follows - starting three to four days prior to rolling.
2 or 3 5HTP pills per day including the day of the drop.
1 Multivitamin per day including day of drop.
1 Magnesium, B-Vit Complex Pill per day including day of drop.
All of the above taken together with a large glass of grapefruit juice.
Also, at least 25g of dark chocolate each day.
Diet is also important - good healthy foods: chicken, potatoes, veg, fruit etc.
On day of drop:
Stop eating 6 - 8 hours before you roll.
Drink several strong cups of green tea.
One hour before dropping, take a couple of antacid tablets.
This is very basic, if you search the forum there are proper guides and people take this very seriously. However, the above should all help your roll and, more importantly, help manage the comedown and reduce harm (at least to a limited extent).
As for doses impossible and inappropriate to say. For myself, my first time was 115mg with a top up of 35mg and that was enough for an evening of 10pm till 5:30am. Second time, some months later, I did a lot more. 140mg then 50mg then another 80mg several hours after. Wish I had taken a higher initial dose and topped up less. However, it will depend on when you rolled last. The more often you roll the more the stuff you need. If you pre-load, you won't need as much to get high.