1 gold florin weighted 3.54g, so you would have 282,5 golden florins.
Now, how much was a florin worth? Quite a bit. In 1414 a cashier placed in a position of trust in a bank in Florence would earn 50 florins a year, a clerk 40, an office boy 15. The annual rent of an house in a nice neighbrohood would have been 20-30 florins.

A venetian ducat was worth roughly the same of a florin, and in 1474 a Milan councillor would have a yearly salary of 240 ducats, while a house worth of him would cost between 1200 and 1600 ducats.
The highest priced slaves were young women in their early 20s and during the early 1400 they would cost 60-70 florins in Florence, while the average place of a slave was 30.

So in the end 282 florins would be the equivalent of more than a year salary of a very wealthy man, 5 year salary of a professionist and more than 10 times that of an average unskilled young laborer.
Sadly I have no idea about investments. I hope this will be enough.

Sources:
The Rise and Decline of the Medici Bank: 1397-1494, Raymond De Roove (1999)
A Renaissance Court: Milan under Galleazzo Maria Sforza, Gregory Lubkin (1994)

Golden hyperpyron (gold currency of Byzantine Empire after Alexios Komnenos, the founder of the Komnenos Dynasty) gradually fell into disuse starting from early 14th century. As /u/Arcadess pointed out, currencies like Florin and Venetian Ducat have become popular.

Now, I'm not an expert on 15th century Byzantine Constantinople but I can help with 15th century Ottoman Constantinople.

After the fall/conquest of Constantinople in 1453, Mehmed II (Fatih/Conqueror) issued golden coins (sultani) based on Venetian Ducat. 1 sultani from 1470's weighted 3,57g. (You'd have ~280 sultanis with 1kg gold)

If you had 1 sultani, you could buy 0,3kg of finest raw silk[1] or ~30kg of meat[2] in 1470's.

Could a man with 282 ducats/florins purchase the services of many mercenaries? by /u/Darth_Cosmonaut_1917

I'm not sure about mercenaries but here's a boring version of your scenario: If you had 1 sultani, you could hire an unqualified worker for 10 days (or a stonemason/carpenter for 5 days).

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[1]An Economic and Social History of the Ottoman Empire, Halil Inalcik

[2]A Monetary History of the Ottoman Empire, Sevket Pamuk