Hi @bbsin
1. To show clickable link in Gallery
Insert a HtmlText and Set HtmlText to
"<a style='color:blue' href='" & ThisItem.URLColumn & "'>" & ThisItem.URLColumn & "</a>"

2. For Currency, As Ram mentioned needs to convert to value since PowerApps has text
Patch(
EventIItinerary,
BrowseGallery1.Selected,
{
Cost: Value(DataCardValue15.Text),
EventLogin: DataCardValue16.Text
}
)
3. To Save back the URL, no special needed. This is just text
EventLogin: DataCardValue16.Text
here EventLogin is URL field in Sharepoint
Please share the error information if this is not resolved.